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.Data/Wire.cs

@@ -13,8 +13,6 @@ namespace ClaudeDo.Data.Wire;
 
 public record ActiveTaskDto(string Slot, string TaskId, DateTime StartedAt);
 
-public record WorkerBuildInfoDto(string? BuildSha);
-
 public record AppSettingsDto(
     string DefaultClaudeInstructions,
     string DefaultModel,