fix(ui): suppress auto-open conflict resolver during MCP-driven merges

review_task/continue_merge on a planning parent always leaves conflicts in
the tree, and the UI auto-opened the resolver on every PlanningMergeConflict
broadcast regardless of who started the merge -- so a running Claude session
resolving a unit-merge conflict could race a human editing the same shared
checkout in a resolver window neither of them asked for.

PlanningMergeOrchestrator.StartAsync now takes an externallyDriven flag (set
by ExternalMcpService's MCP-driven review_task path, left false for the UI's
ApproveReview) that rides along on the PlanningMergeConflict broadcast. The
UI only auto-opens the resolver when it's false; otherwise it shows a
persistent banner with a manual "Open resolver" button, cleared on
PlanningMergeAborted/PlanningCompleted. A new GetActiveExternalConflictsAsync
query (checked against GitService.IsMidMergeAsync rather than the in-memory
flag alone) lets the UI resync the banner on reconnect instead of trusting a
one-shot broadcast that isn't replayed after a restart.

The childless single-task conflict path was checked and needed no change --
it only broadcasts the generic TaskUpdated, never PlanningMergeConflict.

src/ClaudeDo.Worker/Planning/PlanningMergeOrchestrator.cs

@@ -10,6 +10,9 @@ using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
 
 namespace ClaudeDo.Worker.Planning;
 
+/// <summary>A unit-merge conflict currently paused, driven by an MCP session rather than the UI.</summary>
+public sealed record ExternalPlanningMergeConflict(string PlanningTaskId, string SubtaskId);
+
 public sealed class PlanningMergeOrchestrator
 {
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
@@ -25,6 +28,11 @@ public sealed class PlanningMergeOrchestrator
         public required string TargetBranch { get; init; }
         public required Queue<string> RemainingSubtaskIds { get; init; }
         public required bool IsPlanning { get; init; }
+        public required string WorkingDir { get; init; }
+        /// <summary>True when this unit merge was started by an MCP tool call (e.g. review_task
+        /// from a running Claude session) rather than a direct UI action. Conflicts on such a
+        /// merge must not auto-pop the in-app resolver — the driving session owns resolution.</summary>
+        public required bool ExternallyDriven { get; init; }
         public string? CurrentSubtaskId { get; set; }
     }
 
@@ -48,7 +56,8 @@ public sealed class PlanningMergeOrchestrator
         _logger = logger;
     }
 
-    public async Task StartAsync(string parentTaskId, string targetBranch, CancellationToken ct)
+    public async Task StartAsync(
+        string parentTaskId, string targetBranch, CancellationToken ct, bool externallyDriven = false)
     {
         string workingDir;
         List<TaskEntity> children;
@@ -100,7 +109,14 @@ public sealed class PlanningMergeOrchestrator
 
         var queue = new Queue<string>(idsToMerge);
 
-        var state = new State { TargetBranch = targetBranch, RemainingSubtaskIds = queue, IsPlanning = isPlanning };
+        var state = new State
+        {
+            TargetBranch = targetBranch,
+            RemainingSubtaskIds = queue,
+            IsPlanning = isPlanning,
+            WorkingDir = workingDir,
+            ExternallyDriven = externallyDriven,
+        };
         if (!_states.TryAdd(parentTaskId, state))
             throw new InvalidOperationException($"Merge already in progress for {parentTaskId}.");
 
@@ -112,6 +128,23 @@ public sealed class PlanningMergeOrchestrator
     public bool HasActiveMerge(string parentTaskId) =>
         _states.TryGetValue(parentTaskId, out var s) && s.CurrentSubtaskId is not null;
 
+    /// <summary>Externally-driven unit merges currently paused on a conflict, so the UI can
+    /// recover this on reconnect instead of relying solely on the one-shot broadcast. Checked
+    /// against <see cref="GitService.IsMidMergeAsync"/> rather than trusting the in-memory flag
+    /// alone, so a stale entry (e.g. the repo was already resolved through another path) never
+    /// reports an external merge that no longer exists.</summary>
+    public async Task<IReadOnlyList<ExternalPlanningMergeConflict>> GetActiveExternalConflictsAsync(CancellationToken ct)
+    {
+        var result = new List<ExternalPlanningMergeConflict>();
+        foreach (var (planningTaskId, state) in _states)
+        {
+            if (!state.ExternallyDriven || state.CurrentSubtaskId is null) continue;
+            if (!await _git.IsMidMergeAsync(state.WorkingDir, ct)) continue;
+            result.Add(new ExternalPlanningMergeConflict(planningTaskId, state.CurrentSubtaskId));
+        }
+        return result;
+    }
+
     public async Task ContinueAsync(string planningTaskId, CancellationToken ct)
     {
         if (!_states.TryGetValue(planningTaskId, out var state) || state.CurrentSubtaskId is null)
@@ -123,7 +156,7 @@ public sealed class PlanningMergeOrchestrator
 
         if (result.Status == TaskMergeService.StatusConflict)
         {
-            await _broadcaster.PlanningMergeConflict(planningTaskId, current, result.ConflictFiles);
+            await _broadcaster.PlanningMergeConflict(planningTaskId, current, result.ConflictFiles, state.ExternallyDriven);
             return;
         }
 
@@ -200,7 +233,8 @@ public sealed class PlanningMergeOrchestrator
 
                 if (result.Status == TaskMergeService.StatusConflict)
                 {
-                    await _broadcaster.PlanningMergeConflict(planningTaskId, subtaskId, result.ConflictFiles);
+                    await _broadcaster.PlanningMergeConflict(
+                        planningTaskId, subtaskId, result.ConflictFiles, state.ExternallyDriven);
                     keepState = true;
                     return;
                 }