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/Interfaces/IWorkerClient.cs

@@ -183,9 +183,6 @@ public interface IWorkerClient : INotifyPropertyChanged
     Task<string> GetLastPrepLogAsync();
     Task<IReadOnlyList<WorkerLogEntry>> GetRecentLogsAsync();
 
-    /// <summary>Git SHA the running worker was built from (null when offline or the build isn't stamped).</summary>
-    Task<WorkerBuildInfoDto?> GetWorkerBuildInfoAsync();
-
     Task<List<PrimeScheduleDto>> GetPrimeSchedulesAsync();
     Task<PrimeScheduleDto?> UpsertPrimeScheduleAsync(PrimeScheduleDto dto);
     Task DeletePrimeScheduleAsync(Guid id);