feat(queue): warn when the base branch has uncommitted changes

Queuing (update_task_status, batch_update_task_status) and run_task_now
now surface a non-blocking baseDirty warning (separate modified/untracked
counts) when the list's working dir has uncommitted changes at enqueue
time, since a new worktree forks from the commit tip and silently misses
them. BaseDirtyChecker caches per working dir for a few seconds so a
batch queue over many tasks in one list only shells out to git once. The
UI surfaces the same warning via the footer error strip on queue actions.

src/ClaudeDo.Worker/Hub/WorkerHub.cs

@@ -88,6 +88,8 @@ public record ForceRemoveResultDto(bool Removed, string? Reason);
 public record PlanningMergeConflictStateDto(string PlanningTaskId, string SubtaskId);
 public record PendingQuestionDto(string TaskId, string QuestionId, string Question);
 public record MergeResultDto(string Status, IReadOnlyList<string> ConflictFiles, string? ErrorMessage);
+public record BaseDirtyWarningDto(int ModifiedCount, int UntrackedCount);
+public record SetTaskStatusResultDto(BaseDirtyWarningDto? BaseDirty);
 public record MergePreviewDto(string Status, IReadOnlyList<string> ConflictFiles, int ChangedFileCount);
 public record MergeTargetsDto(string DefaultBranch, IReadOnlyList<string> LocalBranches);
 public record MergeConflictDocumentsDto(string TaskId, IReadOnlyList<ConflictDocumentDto> Files);
@@ -706,7 +708,7 @@ public sealed class WorkerHub : Microsoft.AspNetCore.SignalR.Hub
         return new ListConfigDto(config.Model, config.SystemPrompt, config.AgentPath, config.MaxTurns, SkillsFromJson(config.SessionSkills), config.VerifyCommand);
     }
 
-    public async Task SetTaskStatus(string taskId, string status)
+    public async Task<SetTaskStatusResultDto> SetTaskStatus(string taskId, string status)
     {
         if (!Enum.TryParse<TaskStatus>(status, ignoreCase: true, out var parsed))
             throw new HubException($"unknown status: {status}");
@@ -716,6 +718,8 @@ public sealed class WorkerHub : Microsoft.AspNetCore.SignalR.Hub
             ? await _state.EnqueueAsync(taskId, Context.ConnectionAborted)
             : await _state.ForceSetStatusAsync(taskId, parsed, Context.ConnectionAborted);
         if (!result.Ok) throw new HubException(result.Reason ?? "set status failed");
+        return new SetTaskStatusResultDto(
+            result.BaseDirty is { } w ? new BaseDirtyWarningDto(w.ModifiedCount, w.UntrackedCount) : null);
     }
 
     public Task<MergeResultDto> ApproveReview(string taskId, string targetBranch)