Say how far a connection has got while it is still being made

The connecting card set its status string once, when the tab was created, and
never touched it again. Every connection therefore looked identical from the
outside: one three seconds into a key exchange, one waiting out a fifteen-second
timeout against a machine that is asleep, and one that had hung all drew the
same "connecting…". The card now draws the five steps of getting there, each lit
at the moment the handshake reports reaching it, over an amber track that fills
as they finish.

◆ NOTHING ON THE LIST IS INVENTED. Every row changes state because a layer below
it said so, at the instant the thing it names actually began.

That is the whole reason it is worth showing, and it is why most of this commit
is plumbing rather than XAML: there was no progress reporting anywhere in the
stack to hook a step list onto, and a card animating plausible progress would
have been indistinguishable from one that had stopped receiving any.

SshConnectionPhase names four phases and deliberately not more. SSH.NET runs the
entire handshake inside one ConnectAsync and raises exactly one event from the
middle of it — HostKeyReceived, once the key exchange has produced a key to show
— so that event is the only interior moment there is to report. Everything
before it is Reaching and everything after it is Authenticating. A fifth phase
in that assembly would have to be a timer, so there is not one. OpeningShell is
reported by TerminalWorkspace instead, because that is where it happens: the
factory's work ends with an authenticated connection, and asking for a
pseudo-terminal on one is a separate round trip. The SFTP path passes null — a
second connection opened behind an already-open shell has nobody watching a step
list for it.

The card's fifth step, "Starting the terminal", is the renderer wait and lives
in the shell rather than in the SSH assembly, which has never heard of a
renderer. On the first connection after a cold start it is a real wait with a
real failure mode of its own — a missing WebView2 runtime — so a list that began
at "reaching the host" would leave the one wait most likely to hang unnamed.

Amber for the step in flight, and that follows the palette's rule rather than
bending it. Green is what is true and purple is what you can press; a step still
happening is neither, and it is exactly the caveat-worth-reading that amber
exists for. Steps behind it go green as they become true. Nothing animates,
which is the argument TransfersScreen.axaml already makes for its own track,
reaching a screen with far more reason to want a spinner: a spinner is furniture
invented to fill a state nobody measured, and these states are measured, so the
track fills to what has finished and then waits there.

A refusal keeps the step it stopped on, in red, with the ones behind it still
green. That is the half a progress bar could not do, and it is the difference
between "that host is not there" and "that host is there and would not have me"
— a question the reason sentence alone frequently does not settle.

The strip's dot goes amber while a tab is connecting, on both heads. It was
grey, and so is a tab whose shell has exited: the two states in that strip with
the least in common, one worth waiting for and one over. PhoneShell's own
comment already recorded half of this — the dot stopped being green before
anything had answered — and this is the other half.

Progress is raised inline rather than through System.Progress<T>, which captures
whatever synchronisation context it was constructed on and posts to it. That
reads like a convenience and is really a second place the marshalling decision
gets made: silently, differently under a test with no context, and out of order
with respect to the failure that follows a phase. The shell marshals once, in
one handler, through a new optional post parameter on MainWindowViewModel — the
same seam TransfersViewModel already uses, and for the reason its own remark
gives. The three Dispatcher.UIThread.Post calls that predate it are the ones
this suite's comments record as out of reach; they are left alone rather than
swept in here.

Both heads draw the list. They differ in one place: Phone.axaml's mono class
sets a colour and a size along with the family, so the caption rule names its
own family instead of composing the two and asking two rules for one Foreground.
The desktop's mono sets the family alone, which is why ConnectingCard does
compose them. Each head also gains SHOW LOGS beside the button that gives up —
the step list is this attempt and the log is every other one, which is what a
connection taking too long actually raises.

Seven tests, and the two that matter most run against the container rather than
a fake: a real handshake reports its phases in order, and a host-key refusal
never claims to have authenticated. A fake asserting what it was written to
assert would have established nothing about either. The rest cover the tab
advancing while the connection is gated, the step a refusal stops on, and a
phase reported after the user has given up on the tab. 1,861 tests, none
failing.

The Android head's layout is not verified by anything. It compiles, and
compiled bindings mean every new binding path resolves, but that project is not
in DodoSSH.slnx, there is no test project for it and no device here — so unlike
the desktop card, whose shapes the layout harness measures, these rows have not
been drawn. Vertical fit is reasoned, not observed.

src/DodoSSH.Client.Shell/ViewModels/MainWindowViewModel.cs

@@ -328,6 +328,9 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
     /// </remarks>
     private readonly Func<string, Task>? copyToClipboard;
 
+    /// <inheritdoc cref="MainWindowViewModel(ClientPaths, ClientCacheFactory, TerminalWorkspace, VaultKnownHostStore, IDeviceKeyStore, SignInHandler, TimeProvider, ISftpSessionFactory, Argon2Profile?, ResumeHandler?, Func{string, Task}?, string?, IUpdateChannel?, Action{Action}?)" path="/param[@name='post']" />
+    private readonly Action<Action> post;
+
     /// <remarks>
     /// Created once and kept for the life of the process, like <see cref="workspace"/> and for the same
     /// reason: file transfer opens its own authenticated connection, and locking the vault must not destroy
@@ -470,6 +473,19 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
     /// absence of a line rather than by a line somebody has to remember to keep a no-op; and ADR 0011 settles
     /// the Android head's distribution separately, so it must never acquire one by accident.
     /// </param>
+    /// <param name="post">
+    /// Runs an action on the thread this shell's view models are read from. Defaults to the UI thread's
+    /// dispatcher, which is the answer in every real head.
+    /// <para>
+    /// A delegate rather than <c>Dispatcher.UIThread</c> reached directly, for exactly the reason
+    /// <c>TransfersViewModel</c>'s is one — see the remark there. It is process-wide and belongs to whichever
+    /// thread touched it first, so a suite that runs with no window has no way to drain it and no way to
+    /// know whose it is. This one exists because connection phases are reported from the handshake's own
+    /// thread, which is the first thing in this class that has to cross onto the UI thread and also has to
+    /// be assertable: the three <c>Dispatcher.UIThread.Post</c> calls that predate it are the ones this
+    /// suite's own comments record as out of reach, and they are left alone rather than swept in here.
+    /// </para>
+    /// </param>
     internal MainWindowViewModel(
         ClientPaths paths,
         ClientCacheFactory caches,
@@ -483,8 +499,11 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
         ResumeHandler? resume = null,
         Func<string, Task>? copyToClipboard = null,
         string? deviceName = null,
-        IUpdateChannel? updates = null)
+        IUpdateChannel? updates = null,
+        Action<Action>? post = null)
     {
+        this.post = post ?? (action => Dispatcher.UIThread.Post(action));
+
         this.paths = paths;
         this.caches = caches;
         this.workspace = workspace;
@@ -3243,7 +3262,7 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
             oldValue.PropertyChanged -= OnVaultPropertyChanged;
             oldValue.Hosts.CollectionChanged -= OnVaultHostsChanged;
 
-            // The three connection events are kept while an attempt is still in flight, and that is not an
+            // The four connection events are kept while an attempt is still in flight, and that is not an
             // oversight. Locking does not end a handshake any more than it ends a shell — the workspace is
             // what holds both, and it outlives every vault — so a connection started just before a lock still
             // has an answer coming, and the tab standing in for it is still in the strip afterwards, because
@@ -3257,6 +3276,7 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
             if (attempts.Count == 0)
             {
                 oldValue.ConnectionStarting -= OnVaultConnectionStarting;
+                oldValue.ConnectionProgress -= OnVaultConnectionProgress;
                 oldValue.ConnectionFailed -= OnVaultConnectionFailed;
                 oldValue.SessionOpened -= OnVaultSessionOpened;
             }
@@ -3265,6 +3285,7 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
         if (newValue is not null)
         {
             newValue.ConnectionStarting += OnVaultConnectionStarting;
+            newValue.ConnectionProgress += OnVaultConnectionProgress;
             newValue.ConnectionFailed += OnVaultConnectionFailed;
             newValue.SessionOpened += OnVaultSessionOpened;
             newValue.PropertyChanged += OnVaultPropertyChanged;
@@ -3406,6 +3427,41 @@ internal sealed partial class MainWindowViewModel : ObservableObject, IAsyncDisp
         AdoptTab(tab);
     }
 
+    /// <summary>
+    /// Moves a connecting tab's step list on, from the handshake's own report.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The one place the phases raised by <c>VaultViewModel.ConnectionProgress</c> are marshalled, and the
+    /// reason that event does not marshal for itself: doing it here means it happens once, visibly, at the
+    /// only boundary that cares — everything this touches is a view model an Avalonia binding is attached to.
+    /// </para>
+    /// <para>
+    /// Posted unconditionally rather than applied inline when it looks safe. Some phases really do arrive
+    /// on this thread — the first is reported before the handshake has yielded at all — and a
+    /// <c>CheckAccess</c> fast path for them would buy one dispatcher turn on a card that is up for seconds,
+    /// at the price of the two orderings existing at once and only one of them being the one a test runs.
+    /// </para>
+    /// <para>
+    /// A step that arrives after the attempt has settled is harmless and needs no guard here:
+    /// <see cref="TerminalTabViewModel.Advance"/> ignores anything reported to a tab that is no longer
+    /// connecting, which is what a posted phase landing behind its own <see cref="OnVaultSessionOpened"/>
+    /// looks like.
+    /// </para>
+    /// <para>
+    /// A report for an attempt with no tab is dropped, exactly as the other two handlers drop one: the user
+    /// closed the connecting tab and there is nothing left to draw a step on. The handshake is not affected
+    /// and its session is still adopted if it opens.
+    /// </para>
+    /// </remarks>
+    private void OnVaultConnectionProgress(object? sender, ConnectionProgressEventArgs e) => post(() =>
+    {
+        if (attempts.TryGetValue(e.AttemptId, out var tab))
+        {
+            tab.Advance(e.Step);
+        }
+    });
+
     /// <summary>
     /// Redraws the vault menu after a synchronisation pass found a vault this account had not seen.
     /// </summary>