refactor(ui): remove the stale-worker banner

The banner compared the running worker's build SHA against the
selected list's HEAD via a git ancestor check on every list switch
and reconnect. It added a git-rev-parse MSBuild target, a hub call,
and a poll loop for a corner case that hasn't come up in practice —
not worth the moving parts.

src/ClaudeDo.Ui/Services/WorkerClient.cs

@@ -492,9 +492,6 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
     public async Task<string> GetLastPrepLogAsync()
         => await TryInvokeAsync<string>("GetLastPrepLog") ?? string.Empty;
 
-    public Task<WorkerBuildInfoDto?> GetWorkerBuildInfoAsync()
-        => TryInvokeAsync<WorkerBuildInfoDto>("GetWorkerBuildInfo");
-
     public async Task<IReadOnlyList<WorkerLogEntry>> GetRecentLogsAsync()
         => await TryInvokeAsync<List<WorkerLogEntry>>("GetRecentLogs") ?? new List<WorkerLogEntry>();