Free the terminal from the Hosts screen, and fill the room it left

The WebView sat inside the Hosts grid, so navigating to Files or the keychain
hid every open terminal and the strip that named them. A connection you had
opened was invisible from four of the five screens. The window now has two
surfaces rather than one: a nav rail that says which page you are on, and a
terminal strip that is always there and switches the whole content area to a
shell. Screen keeps meaning "which page" and never becomes a sixth kind of
page, which is why this is two properties instead of one enum with a terminal
member in it.

Every screen lives inside one wrapper panel that collapses when a terminal is
showing. That is not tidiness — the WebView hosts a Win32 child window that
composites above everything Avalonia draws, so a screen left visible over its
rectangle is a screen sliced in half, and this window has shipped that defect
once already. One decision point, IsTerminalShowing, and a nested panel rather
than five compound bindings nobody would remember to extend.

The focus choreography is the part no test in this repo can see. Every reveal
path now focuses in the same turn the WebView appeared, so all three of them
post at DispatcherPriority.Loaded and let the native control re-push its bounds
first. Going the other way had a real bug: the screen-changed branch called a
bare Focus() where it had to release the keyboard from the native child, so
switching from a terminal to Files silently ate the first keystrokes. Rare
before this commit and the primary gesture after it.

The tab strip grew a cross inside each tab, a plus that opens the quick-connect
palette, and middle-click close. Nested buttons are correct here: Avalonia
handles a left press on the cross and deliberately does not handle other
buttons, which is exactly what lets middle-click bubble up from the cross as
well as the tab. The test is PointerUpdateKind rather than
IsMiddleButtonPressed, because the latter reports button state and is also true
for a left press made while the middle button happens to be held. The handler
is on the tab and not the strip, so the background closes nothing by
construction. Plus opens the palette rather than a flyout, since a menu
dropping into the WebView's rectangle may or may not composite above a child
HWND and this repo does not make rendering claims it has not photographed.

Everything a user reads now says keychain. The wire, the database and the
cryptographic spec still say vault, deliberately: renaming those is a migration
and a protocol change for a word. That split is written down rather than left
to be rediscovered as an inconsistency.

Four things that were squeezed into the keychain's category rail, or into
nothing at all, now have screens. Pinned host keys get one, with fingerprints
never truncated and a filter that matches them, because comparing what you have
against what the operator published is the whole workflow; the approved date is
read out of the item's UUIDv7 rather than added as a column, and says so, since
it means first approval and not last use. Keys can be generated in the client,
which needed the openssh-key-v1 container written by hand — there is no BCL or
NSec helper, and the PKCS#8 route is unverified in the SSH library this uses.
The armour carries no passphrase: encrypting it needs bcrypt_pbkdf, which is
Blowfish with a swizzle, in a project whose crypto is otherwise entirely
libsodium, for a protection the key's own remarks argue is redundant inside a
vault. Generation fills the existing editor and stops, so SAVE stays the one
thing that writes. ~/.ssh/config can be imported behind a preview that is
ticked per row and writes nothing until the button; IdentityFile records the
path and imports the key material only on an explicit opt-in, because reading
somebody's private key into a vault is precisely the act this product exists to
make deliberate. Match blocks and ProxyJump are reported rather than obeyed —
one cannot be evaluated statically and the other has nothing behind it to route
with, and a preview that implied otherwise would be worse than one that admits
it.

Files can be dragged in all four directions that are honestly available. Remote
to Explorer does not ship and is not pretended to: the shell wants the bytes
during the drop, which needs a virtual file and a native COM data object,
outside what Avalonia offers. Note for the next person that Avalonia 12
replaced the drag model outright — DataObject and DataFormats are no-op stubs
and IDataObject is not in the reference assembly, so every tutorial written for
11 does not compile here.

Hosts can be grouped, flat and never nested. A parent id merged as a scalar
lets two offline clients each re-parent A under B and B under A, producing a
cycle inside an encrypted payload that no server can police and every reader
would have to detect for ever. Membership lives in that payload rather than in
the one plaintext concession ADR 0001 allows, whose test is that the relay
cannot function without it — nothing on the server reads a group, so what
plaintext would hand over is a clustering of the estate for nothing. The
plaintext column reserved for it is dropped, provably always null, and the
server now refuses a client that sends one; it was never populated, was copied
on apply, and was not cleared on delete, so a group id would have outlived the
host it described.

Snippets insert through xterm rather than through the pump, because xterm is
the only thing that knows whether the remote has bracketed paste on, and that
is what makes a shell treat embedded newlines as text instead of as execute.
The host process moves opaque bytes and never parses output, so it would have
to guess, and guessing wrong runs every line. Running is off by default and the
copy says the text goes into whatever is there — the terminal has no notion of
being at a prompt, and may be in vi or at a password prompt with echo off, so
the Enter the user presses themselves is the entire safety property.

Connections and keychain changes are recorded as synced encrypted items, which
is what makes them auditable by a team later and costs the server knowledge of
connection rate and timing from row counts alone. ADR 0001 already concedes it
cannot hide that class of metadata; the trade is now written into it rather
than left implicit. A connection entry is written once, at close, which is what
makes a synced log tractable: nothing to merge, one outbox row, no chance of
colliding with itself. Live sessions come from memory, not from the log. The
write is void by contract and posts to a bounded channel, because putting an
encrypt-and-write on the teardown path of every session is how closing the
application comes to take four seconds. A ticket opened before a lock still
closes afterwards, since a shell outlives the vault. The activity log hooks the
one generic repository every kind writes through, so it cannot miss a caller —
which is also why the log kinds themselves declare they are not audited, or the
first entry would write an entry about writing an entry. It records the names
of the fields that changed and never their values; a log with an old password
in it would be a plaintext credential store with no vault around it. Retention
is 90 days or 5,000 entries, whichever bites first, pruned on the sync loop
rather than on a second timer.

That log traffic then broke the status line, which is worth recording because
the fix is a shape and not a patch: background sync counted its own log rows as
pushed items, so the quiet rule stopped being quiet and every action's message
was overwritten a second later by a sync report. The report now separates log
rows from user items and the rule reads the latter.

S3 buckets appear as a remote in the file browser, behind the same interface an
SFTP session implements, so the queue and both panes did not have to learn what
they are talking to. Uploads go through a pipe, because the queue wants to
write and the SDK wants to read; memory is then bounded by the part size
instead of buffering a file to disk twice.

Finally, the Windows device key store moved out of the session project, which
was the one thing keeping it from being portable — everything else in it is
platform-neutral, and a Windows CNG dependency in the middle of the vault code
meant a second head could not reference it without dragging Windows along. The
seam that made the move free was already there. docs/android-port.md is the
audit behind that: what ports, what does not, in order of cost, the four
decisions taken, and an inventory of every screen and state the interface has
to carry, written so a design can be made from it directly.

dotnet build, dotnet test and dotnet format --verify-no-changes are all clean:
1240 tests at zero warnings, including the end-to-end suite against real
containers. The manual checks that headless Avalonia cannot make — the drag
from Explorer, a generated key against a real host, twelve tabs at the minimum
window width — are listed in docs/manual-checks.md and are still outstanding.

src/DodoSSH.Client.App/ViewModels/KnownHostsViewModel.cs

@@ -0,0 +1,235 @@
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.Globalization;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using DodoSSH.Client.Domain;
+using DodoSSH.Client.Sync;
+
+namespace DodoSSH.Client.App.ViewModels;
+
+/// <summary>One pinned host key, as a row in the list.</summary>
+/// <remarks>
+/// <para>
+/// The only list of the four whose rows nobody created on purpose. A pin appears because somebody approved a
+/// fingerprint at the moment of connecting, and it outlives whatever they approved it for — deleting a host
+/// leaves its pin, and so does changing a host's address. Both are correct as <em>trust</em> decisions: the
+/// address may still be reached by another host, and a pin is about the endpoint rather than the bookmark.
+/// What was wrong was that nothing ever showed them.
+/// </para>
+/// <para>
+/// Nothing here is secret. A host key fingerprint is published by operators on purpose, and the whole point
+/// of pinning one is to compare it with what they published.
+/// </para>
+/// </remarks>
+internal sealed class KnownHostRowViewModel(VaultItem<KnownHostSecret> pin, bool isDialledByAHost)
+{
+    internal Guid EntityId => pin.EntityId;
+
+    internal KnownHostSecret Pin => pin.Secret;
+
+    internal string Host => pin.Secret.Host;
+
+    internal int Port => pin.Secret.Port;
+
+    internal string Algorithm => pin.Secret.Algorithm;
+
+    /// <summary>The endpoint and algorithm, which is what a pin actually identifies.</summary>
+    internal string Label => pin.Secret.Label;
+
+    /// <summary>The fingerprint, in full.</summary>
+    /// <remarks>
+    /// Not truncated. The only thing anybody does with a fingerprint is compare it against one an operator
+    /// published, and a shortened one cannot be compared — it can only be glanced at, which is the habit
+    /// this whole mechanism exists to replace.
+    /// </remarks>
+    internal string Fingerprint => pin.Secret.Fingerprint;
+
+    /// <summary>
+    /// Whether any host in this vault actually dials the endpoint this pin is for.
+    /// </summary>
+    /// <remarks>
+    /// The reason this list exists rather than a plain enumeration. It is a hint and not a verdict: reaching
+    /// a machine without a bookmark for it is ordinary, so an unmatched pin is worth pointing at and not
+    /// worth deleting on the user's behalf.
+    /// </remarks>
+    internal bool IsDialledByAHost { get; } = isDialledByAHost;
+
+    internal bool HasUnsyncedChanges => pin.HasUnsyncedChanges;
+
+    internal string Badge => IsDialledByAHost
+        ? ItemBadge.For(pin.IsBlocked, pin.IsReadOnly, pin.HasUnsyncedChanges)
+        : "no host uses this";
+
+    /// <summary>
+    /// When this pin was approved, as far as anything here can tell.
+    /// </summary>
+    /// <remarks>
+    /// Derived from the entity id, which this client mints with <see cref="Guid.CreateVersion7()"/> — see
+    /// <see cref="Uuid7Timestamp"/>. No vault item carries a timestamp, so the alternative was no column at
+    /// all. Two honest limits, both stated on the screen rather than only here: it is when the pin was
+    /// created and not when it was last re-approved, and an id minted by anything that does not use v7
+    /// renders as a dash rather than as a guess.
+    /// </remarks>
+    internal string Approved => Uuid7Timestamp.Of(EntityId) is { } stamped
+        ? stamped.ToLocalTime().ToString("d MMM yyyy", CultureInfo.CurrentCulture)
+        : "—";
+}
+
+/// <summary>
+/// The host keys this keychain has approved, and how to withdraw one.
+/// </summary>
+/// <remarks>
+/// <para>
+/// <b>A wrapper over the vault rather than a view model of its own.</b> Everything about a pin — reading
+/// them, forgetting one, pushing the change — already lives on <see cref="VaultViewModel"/>, wired into its
+/// reload and its automatic sync. Lifting that out would mean re-deriving that wiring and keeping two
+/// copies of it in step. What is genuinely this screen's own is the part below: a filter and the collection
+/// it produces, neither of which the vault has any use for.
+/// </para>
+/// <para>
+/// <b>The filter matches fingerprints, deliberately.</b> The workflow this screen exists for is "the
+/// operator published SHA256:xyz — do I have that one?", and a filter that searched only host names would
+/// answer a question nobody is asking.
+/// </para>
+/// </remarks>
+internal sealed partial class KnownHostsViewModel : ObservableObject
+{
+    private readonly VaultViewModel vault;
+
+    internal KnownHostsViewModel(VaultViewModel vault)
+    {
+        this.vault = vault;
+
+        // The vault rebuilds this list on every reload and every sync pass, and a screen showing a stale
+        // copy of a trust decision is the one kind of staleness that matters here.
+        vault.KnownHostPins.CollectionChanged += OnPinsChanged;
+
+        Rebuild();
+    }
+
+    /// <summary>The pins this filter admits, in the order the vault produced them.</summary>
+    /// <remarks>
+    /// A second collection rather than a filtered view over the first, which is the idiom the host sidebar
+    /// already uses: a view would have to be re-sorted and re-notified anyway, and the vault's own ordering
+    /// — host, then port, then algorithm — is the one worth keeping.
+    /// </remarks>
+    internal ObservableCollection<KnownHostRowViewModel> VisiblePins { get; } = [];
+
+    [ObservableProperty]
+    private string filter = string.Empty;
+
+    /// <summary>The row the list has selected, mirrored onto the vault so its command can act on it.</summary>
+    /// <remarks>
+    /// Pushed down rather than duplicated: <c>ForgetPinCommand</c> reads <c>VaultViewModel.SelectedKnownHost</c>
+    /// and there is no reason for it to learn about this screen.
+    /// </remarks>
+    [ObservableProperty]
+    private KnownHostRowViewModel? selected;
+
+    internal bool HasPins => vault.KnownHostPins.Count > 0;
+
+    internal bool HasVisiblePins => VisiblePins.Count > 0;
+
+    internal bool HasSelection => Selected is not null;
+
+    /// <summary>What the whole list amounts to, in one line.</summary>
+    /// <remarks>
+    /// The unused count is the one worth putting here. A pin nothing dials is not a defect — reaching a
+    /// machine without a bookmark for it is ordinary — but it is the only thing about this list a person
+    /// might want to act on, and counting them is cheaper than reading a badge column.
+    /// </remarks>
+    internal string Summary
+    {
+        get
+        {
+            var total = vault.KnownHostPins.Count;
+
+            if (total == 0)
+            {
+                return string.Empty;
+            }
+
+            var unused = vault.KnownHostPins.Count(pin => !pin.IsDialledByAHost);
+            var pins = total == 1 ? "1 approved host key" : $"{total} approved host keys";
+
+            return unused == 0
+                ? pins
+                : string.Create(CultureInfo.CurrentCulture, $"{pins} · {unused} that no host dials");
+        }
+    }
+
+    internal string EmptyMessage => HasPins
+        ? "No approved host key matches that."
+        : "Nothing approved yet. The first time you connect to a host, its fingerprint is shown for you to "
+            + "check — approving it puts it here.";
+
+    /// <summary>Withdraws trust in the selected pin.</summary>
+    /// <remarks>
+    /// Forwarded, because the vault's version does three things in an order that matters: forget, reload,
+    /// then push. The push is the load-bearing one — the machines still refusing to connect to a rebuilt
+    /// server are the other ones.
+    /// </remarks>
+    [RelayCommand]
+    private async Task ForgetSelectedAsync()
+    {
+        if (Selected is null)
+        {
+            return;
+        }
+
+        await vault.ForgetPinCommand.ExecuteAsync(null).ConfigureAwait(true);
+    }
+
+    internal void Detach() => vault.KnownHostPins.CollectionChanged -= OnPinsChanged;
+
+    partial void OnFilterChanged(string value) => Rebuild();
+
+    partial void OnSelectedChanged(KnownHostRowViewModel? value)
+    {
+        vault.SelectedKnownHost = value;
+        OnPropertyChanged(nameof(HasSelection));
+    }
+
+    private void OnPinsChanged(object? sender, NotifyCollectionChangedEventArgs e) => Rebuild();
+
+    private void Rebuild()
+    {
+        // Captured and restored around the refill, for the reason the host sidebar's rebuild is written the
+        // way it is: Clear() is a Reset the ListBox answers by nulling its own selection, and the binding
+        // writes that null straight back before the refill can matter.
+        var selectedId = Selected?.EntityId;
+
+        VisiblePins.Clear();
+
+        foreach (var pin in vault.KnownHostPins.Where(Matches))
+        {
+            VisiblePins.Add(pin);
+        }
+
+        Selected = VisiblePins.FirstOrDefault(pin => pin.EntityId == selectedId);
+
+        OnPropertyChanged(nameof(HasPins));
+        OnPropertyChanged(nameof(HasVisiblePins));
+        OnPropertyChanged(nameof(Summary));
+        OnPropertyChanged(nameof(EmptyMessage));
+    }
+
+    private bool Matches(KnownHostRowViewModel pin)
+    {
+        if (string.IsNullOrWhiteSpace(Filter))
+        {
+            return true;
+        }
+
+        var needle = Filter.Trim();
+
+        return Contains(pin.Host, needle)
+            || Contains(pin.Algorithm, needle)
+            || Contains(pin.Fingerprint, needle)
+            || Contains(pin.Port.ToString(CultureInfo.InvariantCulture), needle);
+    }
+
+    private static bool Contains(string haystack, string needle) =>
+        haystack.Contains(needle, StringComparison.CurrentCultureIgnoreCase);
+}