fix(worker): mark task Done on every successful merge path, not just approve

Generalizes the previous merge_task fix: the WaitingForReview->Done transition
now lives in TaskMergeService.MergeAsync/ContinueMergeAsync, so the UI Merge
button (WorkerHub.MergeTask), conflict-merge, continue-merge and the external
MCP all land a merged task in Done. ApproveAndMergeAsync no longer double-approves.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -468,12 +468,6 @@ public sealed class ExternalMcpService
 
         if (result.Status == TaskMergeService.StatusMerged)
         {
-            // MergeAsync only flips the worktree to Merged; a merged task must also
-            // reach Done. If it was still awaiting review, approve it now (a Done task
-            // is already terminal and needs no transition).
-            if (task.Status == TaskStatus.WaitingForReview)
-                await _state.ApproveReviewAsync(taskId, cancellationToken);
-
             string? mergeCommit = null;
             try
             {

src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs

@@ -85,6 +85,15 @@ public sealed class TaskMergeService
         await _broadcaster.WorktreeUpdated(taskId);
     }
 
+    private async Task ApproveIfWaitingForReviewAsync(TaskEntity task, CancellationToken ct)
+    {
+        // A merged worktree means the work is integrated, so the task must reach Done.
+        // MarkWorktreeMergedAsync only flips the worktree state; transition the task
+        // itself when it was still awaiting review (a Done task is already terminal).
+        if (task.Status == TaskStatus.WaitingForReview)
+            await _state.ApproveReviewAsync(task.Id, ct);
+    }
+
     public async Task<MergeResult> MergeAsync(
         string taskId,
         string targetBranch,
@@ -168,6 +177,7 @@ public sealed class TaskMergeService
         }
 
         await MarkWorktreeMergedAsync(taskId, ct);
+        await ApproveIfWaitingForReviewAsync(task, ct);
 
         _logger.LogInformation(
             "Merged task {TaskId} branch {Branch} into {Target} (remove worktree: {Remove})",
@@ -187,7 +197,7 @@ public sealed class TaskMergeService
 
     public async Task<MergeResult> ContinueMergeAsync(string taskId, CancellationToken ct)
     {
-        var (_, list, wt) = await LoadMergeContextAsync(taskId, ct);
+        var (task, list, wt) = await LoadMergeContextAsync(taskId, ct);
 
         if (wt is null) return Blocked("task has no worktree");
         if (wt.State != WorktreeState.Active) return Blocked($"worktree state is {wt.State}");
@@ -205,6 +215,7 @@ public sealed class TaskMergeService
         catch (Exception ex) { return Blocked($"commit failed: {ex.Message}"); }
 
         await MarkWorktreeMergedAsync(taskId, ct);
+        await ApproveIfWaitingForReviewAsync(task, ct);
         _logger.LogInformation("Continued merge of task {TaskId} branch {Branch}", taskId, wt.BranchName);
 
         return new MergeResult(StatusMerged, Array.Empty<string>(), null);
@@ -313,12 +324,8 @@ public sealed class TaskMergeService
             ? await _git.GetCurrentBranchAsync(list.WorkingDir, ct)
             : targetBranch;
 
-        var merge = await MergeAsync(taskId, target, removeWorktree: false, $"Merge {wt.BranchName}", ct);
+        // MergeAsync transitions the task WaitingForReview -> Done on a successful merge.
-        if (merge.Status != StatusMerged)
+        return await MergeAsync(taskId, target, removeWorktree: false, $"Merge {wt.BranchName}", ct);
-            return merge;
-
-        var approve = await _state.ApproveReviewAsync(taskId, ct);
-        return approve.Ok ? merge : Blocked(approve.Reason ?? "approve failed");
     }
 
     private static MergeResult Blocked(string reason) =>