feat(worker): add leaveConflictsInTree option to TaskMergeService.MergeAsync

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Worker/Services/TaskMergeService.cs

@@ -45,6 +45,7 @@ public sealed class TaskMergeService
         string targetBranch,
         bool removeWorktree,
         string commitMessage,
+        bool leaveConflictsInTree,
         CancellationToken ct)
     {
         TaskEntity task;
@@ -89,6 +90,11 @@ public sealed class TaskMergeService
             try { files = await _git.ListConflictedFilesAsync(list.WorkingDir, ct); }
             catch { files = new(); }
 
+            if (leaveConflictsInTree && files.Count > 0)
+            {
+                return new MergeResult(StatusConflict, files, null);
+            }
+
             // If abort fails the repo is left mid-merge; the caller must resolve manually.
             // Return Blocked (not conflict) so the UI does not offer a stale conflict list.
             try { await _git.MergeAbortAsync(list.WorkingDir, ct); }
@@ -141,6 +147,14 @@ public sealed class TaskMergeService
         return new MergeResult(StatusMerged, Array.Empty<string>(), cleanupWarning);
     }
 
+    public Task<MergeResult> MergeAsync(
+        string taskId,
+        string targetBranch,
+        bool removeWorktree,
+        string commitMessage,
+        CancellationToken ct)
+        => MergeAsync(taskId, targetBranch, removeWorktree, commitMessage, leaveConflictsInTree: false, ct);
+
     public async Task<MergeTargets> GetTargetsAsync(string taskId, CancellationToken ct)
     {
         TaskEntity task;