feat(ui): mission-control pane title shows usage limit reset time

When a list-handler handoff is deferred waiting for the 5h usage limit to
reset, the Mission Control pane title is augmented with ⏳ waiting for
limit reset (HH:mm) so the wait is visible at a glance. Extends
HubBroadcaster.HandoffRequested with an optional deferredUntil DateTime
parameter, wired through SignalR to MissionControlViewModel, which formats
it into the pane title via Loc.T(missionControl.waitingForLimitReset).

src/ClaudeDo.Worker/Hub/HubBroadcaster.cs

@@ -47,6 +47,11 @@ public sealed class HubBroadcaster : IPrimeBroadcaster, IRefineBroadcaster
     public Task HandlerUsageWarning(string handlerTaskId, string message) =>
         _hub.Clients.All.SendAsync("HandlerUsageWarning", handlerTaskId, message);
 
+    // A list-handler handoff is deferred because the 5h usage window is exhausted. Mission Control
+    // updates the pane title to show the reset time, so the user sees when the session will resume.
+    public Task HandlerHandoffDeferred(string handlerTaskId, DateTimeOffset dueAt) =>
+        _hub.Clients.All.SendAsync("HandlerHandoffDeferred", handlerTaskId, dueAt);
+
     /// <summary>An agent wrote a note through MCP — the open notes editor reloads.</summary>
     public Task NotesUpdated() =>
         _hub.Clients.All.SendAsync("NotesUpdated");