Make Connections the place a connection is made, and put the keychain away

Four changes to the phone, and the last one needed the connect path taking
apart.

**The bottom bar is three entries.** The keychain moved onto the hub, which is
now SETTINGS with a gear rather than MORE with a hamburger. A bottom bar is for
the places a session moves between, and keys, credentials and tags are managed
occasionally and then left alone — which is the shape of everything already
behind that hub. With the keychain on it, "more" stopped being a description of
what is there. `ShellScreen.Vault` joining `IsMoreSurface` is the whole of the
change: the tab that lights, the header that stands down and the back gesture's
first case all read that one property, which is why the switch mirrors it by
construction rather than by a second list. The keychain screen grew the header
every hub screen has, because the shell's own is not above it any more and
without one there would be no back arrow and nothing saying what the list is.

The desktop keeps its Keychain rail entry. A rail with nine slots has room, so
this is the second thing the two heads arrange deliberately differently, after
the hub itself.

**Terminal became Connections**, and the word does more work than a rename
usually does — see below. The enum member stays `ShellSurface.Terminal`, for
the reason the tab was never called Vault: the surface is a terminal, and the
word a user reads is the product's.

**The + puts the software keyboard away.** It sits above a terminal somebody is
typing into, so the sheet it raises was arriving underneath a keyboard covering
the half of the screen the sheet is on — and worse, laid out into the strip
left above it, since the keyboard's inset shortens everything this head draws.
Avalonia cannot do this and it is worth knowing why: `TopLevel.InputPane`
reports the keyboard and offers nothing that closes one, because the framework's
model is that it belongs to whatever has focus — and this keyboard was raised by
the `WebView`'s own text input, by a native view Avalonia's focus manager never
owned. Clearing Avalonia's focus leaves it exactly where it is. So
`Platform/SoftKeyboard.cs` asks `InputMethodManager`, off the decor view's
window token, and every step of it is allowed to be absent.

**With nothing open, Connections is a connect screen rather than an empty
state.** A box taking `user@host` or `user@host:port`, a password, and the
machines most recently connected to underneath. The box is the only path in this
product to a machine the keychain has never heard of, which is a real case it
had no answer for: an address somebody was handed five minutes ago. A typed
password and nothing else — offering the keychain's keys would be a second
binding resolution beside `TryBuildAuthentication`, and the argument against a
second one is written there at length. Nothing typed is saved, and the screen
says so: a machine worth keeping belongs on HOSTS, where it can carry a key, a
group's defaults and a name.

The recents come out of the vault's own connection log rather than a list kept
in this process, so they survive a restart and arrive on a new phone with the
keychain. Deduplicated by address, because this is a list of places and not of
events, and capped at six so the box stays above the keyboard. Emptied when the
vault is — they are decrypted entries naming where somebody works, and a lock
that left them on screen would be a list still readable after every key that
decrypted it was zeroed. Tapping one leads to whichever of two things it is: a
keychain host goes to that host's connect bar, where its key, its password box
and its refusals already live, and an address goes back into the box, without
the password, whose absence is the point of that path rather than a gap in it.

**The connect path was shaped like `HostRowViewModel` all the way down.** The
log entry, the identification, the failure record and the retry all took a row.
They take a four-field `ConnectionTarget` now, so a connection to an address
shares the ladder of refusals, the host-key question and the tab's lifecycle
rather than growing a second copy of them. `ConnectionRecorder.Record` and
`Identify` have always taken a nullable host id, so the log could already hold a
connection with no item behind it.

One behavioural change falls out of that and it is the one to know about:
**trusting a host key now retries the attempt that raised the question** instead
of re-running whichever host is selected. That was correct while a selected host
was the only way to connect; with a manual target it would dial a different
machine, or refuse with "choose a host first" over a key the user has just
agreed to trust. The test selects a host first, so a regression cannot pass by
connecting to the wrong thing successfully.

`LogsViewModel.ReloadAsync` split so the connections half can be read alone.
Reading the keychain's activity for a screen that offers neither would double
the decryption on the list that was already the expensive one.

Twelve tests: the parse grammar as a theory over seven refusals, the dialled
request, the retry, and both branches of tapping a recent row. The recents rows
are built by hand rather than connected-and-closed — what those tests are about
is which branch a row takes, and driving it through the recorder's queue would
test the recorder, which `DodoSSH.Client.Session.Tests` already does. What needs
a device is phases 11.6 to 11.9 of `docs/manual-checks.md`.

src/DodoSSH.Client.Android/Views/PhoneShell.axaml

@@ -56,11 +56,11 @@
       <!--
         The header: which vault, and whether it is synced.
 
-        Hidden behind MORE, and that is the design's arrangement rather than a saving. v2 gives every screen
-        one header carrying that screen's own name and its own actions — a back arrow, an add, a refresh —
-        so the five hub screens draw their own and this one stands down rather than stacking a second row of
-        chrome above theirs. It stays on the two destinations that are the product's top level, where the
-        vault's name and the sync light are the most useful thing a header could say.
+        Hidden behind SETTINGS, and that is the design's arrangement rather than a saving. v2 gives every
+        screen one header carrying that screen's own name and its own actions — a back arrow, an add, a
+        refresh — so the hub screens draw their own and this one stands down rather than stacking a second
+        row of chrome above theirs. What is left is HOSTS, which is the screen the application opens on and
+        the one where the vault's name and the sync light are the most useful thing a header could say.
 
         Wrapped rather than given a second condition, because Avalonia's bindings have no "and": the wrapper
         collapses it over a terminal, where the surface draws its own bar and the vault's name is not what
@@ -241,17 +241,23 @@
 
       <!-- ============ navigation ============ -->
       <!--
-        Gone while a terminal is showing, which is the whole of that surface's arrangement: the bar's four
-        destinations are replaced by a back arrow and a + that leads to three of them, both in the terminal's
+        Gone while a terminal is showing, which is the whole of that surface's arrangement: the bar's three
+        destinations are replaced by a back arrow and a + that leads to all of them, both in the terminal's
         own bar. See TerminalScreen.axaml.
 
         This one is bound directly rather than wrapped — its visibility is a single question and it has no
         second condition of its own to keep separate.
+
+        ── three rather than four ─────────────────────────────────────────────────────────────────────────
+        The keychain moved behind SETTINGS. A bottom bar is for the places a session moves between, and keys,
+        credentials and tags are not that — they are managed occasionally and then left alone, which is the
+        shape of everything else already behind the hub. What is left is the two halves of using this
+        application, and the drawer holding the rest.
       -->
       <Border Grid.Row="3" IsVisible="{Binding IsShowingPages}"
               Background="{StaticResource Chrome}" BorderBrush="{StaticResource Border}"
               BorderThickness="0,1,0,0" Height="64">
-        <Grid ColumnDefinitions="*,*,*,*">
+        <Grid ColumnDefinitions="*,*,*">
 
           <views:NavButton Grid.Column="0" Label="Hosts" Glyph="▤" IsCurrent="{Binding IsHostsShowing}"
                            Command="{Binding ShowScreenCommand}"
@@ -261,31 +267,30 @@
             The terminal is a surface rather than a page — see ShellSurface — so this one does not go
             through ShowScreen. Its own command is on the shell.
 
+            "Connections" rather than "Terminal", and the word does more work than a rename usually does:
+            with nothing open this surface is where a connection is *made* — a machine typed in by hand, and
+            the ones connected to before — so a tab labelled Terminal would name the thing behind the door
+            rather than the door. The enum member stays ShellSurface.Terminal, for the reason the keychain's
+            tab is not called Vault: the surface is a terminal, and the word a user reads is the product's.
+
             The only entry here that never lights, and deliberately no longer tries: this bar is collapsed
             while the terminal is showing, so IsCurrent could only ever be read as false. Binding it anyway
-            would be a rule about a state this control cannot be in. What marks the terminal as current is
-            the surface filling the screen.
+            would be a rule about a state this control cannot be in. What marks it as current is the surface
+            filling the screen.
           -->
-          <views:NavButton Grid.Column="1" Label="Terminal" Glyph="⌗"
+          <views:NavButton Grid.Column="1" Label="Connections" Glyph="⌗"
                            Command="{Binding ShowTerminalCommand}" />
 
           <!--
-            "Keychain", although the design's tab says Vault and the enum member is Vault. The split is a
-            standing rule rather than an inconsistency: every sentence a user reads calls the encrypted
-            store a keychain, and everything under the surface calls it a vault, because renaming the wire
-            route, the tables and the CLR types would put an AAD resource type inside the blast radius of a
-            find-and-replace. See docs/design-import-gaps.md. A tab reading Vault would be the one place the
-            product surface leaked the implementation's word.
-          -->
-          <views:NavButton Grid.Column="2" Label="Keychain" Glyph="⚿" IsCurrent="{Binding IsVaultShowing}"
-                           Command="{Binding ShowScreenCommand}"
-                           CommandParameter="{x:Static vm:ShellScreen.Vault}" />
+            IsMoreSurface rather than IsMoreShowing: this tab stands for seven screens, and a bar that went
+            dark the moment you opened one of them would only ever light two of its three entries.
 
-          <!--
-            IsMoreSurface rather than IsMoreShowing: this tab stands for six screens, and a bar that went
-            dark the moment you opened one of them would only ever light three of its four entries.
+            "Settings" and a gear, where it was "More" and a hamburger. The hub held five destinations and a
+            paragraph and could not be called anything better than More; with the keychain and preferences
+            both on it, it is the place everything that is not connecting to something lives — which is what
+            a gear has meant on a phone since before this application existed.
           -->
-          <views:NavButton Grid.Column="3" Label="More" Glyph="≣" IsCurrent="{Binding IsMoreSurface}"
+          <views:NavButton Grid.Column="2" Label="Settings" Glyph="⚙" IsCurrent="{Binding IsMoreSurface}"
                            Command="{Binding ShowScreenCommand}"
                            CommandParameter="{x:Static vm:ShellScreen.More}" />