feat(ui): add conflict resolution dialog for planning merge-all

Opens a modal when PlanningMergeConflict fires, listing conflicted files
with options to open in VS Code, continue, or abort the merge.

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

src/ClaudeDo.Ui/ViewModels/Planning/ConflictResolutionViewModel.cs

@@ -0,0 +1,83 @@
+using System.Diagnostics;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using ClaudeDo.Ui.Services;
+
+namespace ClaudeDo.Ui.ViewModels.Planning;
+
+public sealed partial class ConflictResolutionViewModel : ObservableObject
+{
+    private readonly IWorkerClient _worker;
+    private readonly string _planningTaskId;
+    private readonly string _worktreePath;
+
+    public string SubtaskTitle { get; }
+    public string TargetBranch { get; }
+    public IReadOnlyList<string> ConflictedFiles { get; }
+
+    [ObservableProperty] private string? _vsCodeError;
+    [ObservableProperty] private string? _actionError;
+
+    public Action? CloseRequested { get; set; }
+
+    public ConflictResolutionViewModel(
+        IWorkerClient worker,
+        string planningTaskId,
+        string subtaskTitle,
+        string targetBranch,
+        IReadOnlyList<string> conflictedFiles,
+        string worktreePath)
+    {
+        _worker = worker;
+        _planningTaskId = planningTaskId;
+        _worktreePath = worktreePath;
+        SubtaskTitle = subtaskTitle;
+        TargetBranch = targetBranch;
+        ConflictedFiles = conflictedFiles;
+    }
+
+    [RelayCommand]
+    private void OpenInVsCode()
+    {
+        try
+        {
+            var args = string.Join(" ", ConflictedFiles.Select(f => $"\"{f}\""));
+            Process.Start(new ProcessStartInfo
+            {
+                FileName = "code",
+                Arguments = args,
+                WorkingDirectory = _worktreePath,
+                UseShellExecute = true,
+            });
+            VsCodeError = null;
+        }
+        catch (Exception ex)
+        {
+            VsCodeError = $"Could not launch VS Code: {ex.Message}. Paths are listed above — copy them manually.";
+        }
+    }
+
+    [RelayCommand]
+    private async Task ContinueAsync()
+    {
+        ActionError = null;
+        try
+        {
+            await _worker.ContinuePlanningMergeAsync(_planningTaskId);
+            CloseRequested?.Invoke();
+        }
+        catch (Exception ex) { ActionError = ex.Message; }
+    }
+
+    [RelayCommand]
+    private async Task AbortAsync()
+    {
+        ActionError = null;
+        try
+        {
+            await _worker.AbortPlanningMergeAsync(_planningTaskId);
+            CloseRequested?.Invoke();
+        }
+        catch (Exception ex) { ActionError = ex.Message; }
+    }
+}