Merge branch 'main' into claude/m3-implementation-57f9d7

Three files conflicted, and two of the resolutions are more than a choice of
side.

QuickConnectTests had both branches fixing the same build break — main's M2
merge left the shell's constructor with an ISftpSessionFactory nobody passed.
Main's version wins because it carries a comment saying why the palette never
needs a session.

VaultSession's conflict is adjacent edits: main added the remembered sign-in
members and this branch changed SyncAsync's summary from "the active vault" to
"one vault". Both kept.

VaultViewModel is the one that matters. Main taught the background pass to
report a sync that had to start over, on the grounds that a machine which
silently re-read a whole vault has had something happen to it; this branch
turned a pass into one report per readable vault. Taking either side alone
would have lost the other, so ResyncedFromStart is now one of the conditions
IsWorthReporting checks, per vault.

Merging also broke something neither branch could have caught alone, and the
build would not have said a word. SyncOnceAsync cleared LastSyncFailed
unconditionally, which was right while a pass was one vault and a failure was
an exception that never reached that line. A failure is now a report — one
unreachable team vault must not stop the others syncing — so the flag was being
cleared over a vault that had just failed, lighting the titlebar SYNCED. It is
computed from the report instead, in the one place both callers go through, so
the manual command gets it as well as the loop. The background pass still
swallows the message and keeps the fact, which is what
AnAutomaticPassThatFails_LeavesTheStatusAlone is there to hold it to.

Two comments the auto-merge left describing a world with one vault in it: the
SCOPES rail's, which said team vaults are refused by the access service, and
the host sidebar's "One heading, for one vault".

tests/DodoSSH.Client.App.Tests/FakeVaultServer.cs

@@ -77,6 +77,16 @@ internal sealed partial class FakeVaultServer : IVaultServer, IAccountApi, ISync
     /// <inheritdoc />
     public SyncOptions SyncOptions => SyncOptions.Default;
 
+    /// <summary>
+    /// The refresh token this "connection" holds.
+    /// </summary>
+    /// <remarks>
+    /// Settable, because rotation is the half of remembering a sign-in that is easy to get wrong: a shell
+    /// that persisted the token it first saw would leave a rotating provider refusing the next launch. A
+    /// test changes this and asserts the new value reaches the cache.
+    /// </remarks>
+    public string? RefreshToken { get; set; } = "refresh-token-1";
+
     /// <inheritdoc />
     public void Dispose()
     {