feat(merge): unify planning conflicts onto the resolver + 3-pane VM foundation

Route planning unit-merge conflicts through ConflictResolverViewModel
(OpenForPlanningAsync) and delete the old ConflictResolutionViewModel dialog.
Add active-file 3-pane reconstruction (MergeFile OursText/TheirsText/ResultText,
ActiveFile, SelectFileCommand, active-file readout) as the VM foundation for the
Rider-style editor. Seam preserved; Ui.Tests 128/128.

src/ClaudeDo.Ui/ViewModels/Conflicts/ConflictModels.cs

@@ -75,4 +75,16 @@ public sealed class MergeFile
     /// <summary>Reassemble the file: stable text verbatim, each conflict replaced by its resolution.</summary>
     public string Compose() => string.Concat(
         Segments.Select(s => s.IsConflict ? (s.Conflict!.Resolution ?? s.Conflict.Ours) : s.StableText));
+
+    /// <summary>Left pane document: stable regions verbatim, conflict regions show Ours text.</summary>
+    public string OursText => string.Concat(
+        Segments.Select(s => s.IsConflict ? s.Conflict!.Ours : s.StableText));
+
+    /// <summary>Right pane document: stable regions verbatim, conflict regions show Theirs text.</summary>
+    public string TheirsText => string.Concat(
+        Segments.Select(s => s.IsConflict ? s.Conflict!.Theirs : s.StableText));
+
+    /// <summary>Middle (result) pane document: stable regions verbatim, conflict regions show Resolution if set, else Ours.</summary>
+    public string ResultText => string.Concat(
+        Segments.Select(s => s.IsConflict ? (s.Conflict!.Resolution ?? s.Conflict.Ours) : s.StableText));
 }

src/ClaudeDo.Ui/ViewModels/Conflicts/ConflictResolverViewModel.cs

@@ -15,6 +15,13 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     private readonly IWorkerClient _worker;
     private readonly string _taskId;
 
+    // The task whose conflicted working tree is read/written. For a single-task merge this is
+    // _taskId; for a planning unit-merge it's the subtask currently being merged.
+    private string _conflictTaskId;
+
+    // When set, this is a planning unit-merge: continue/abort drive the orchestrator on the parent.
+    private string? _planningParentId;
+
     public ObservableCollection<MergeFile> Files { get; } = new();
 
     // All text conflicts across all files, flattened for one-at-a-time navigation.
@@ -38,14 +45,39 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     [NotifyCanExecuteChangedFor(nameof(PreviousCommand))]
     private int _currentIndex = -1;
 
+    [ObservableProperty] private MergeFile? _activeFile;
+
+    /// <summary>Raised when the active file changes so the view can rebuild its three documents.</summary>
+    public event Action? ActiveFileChanged;
+
+    partial void OnActiveFileChanged(MergeFile? value)
+    {
+        ActiveFileChanged?.Invoke();
+        OnPropertyChanged(nameof(ActiveOursText));
+        OnPropertyChanged(nameof(ActiveTheirsText));
+        OnPropertyChanged(nameof(ActiveResultText));
+        OnPropertyChanged(nameof(PositionText));
+    }
+
+    public string ActiveOursText   => ActiveFile?.OursText   ?? "";
+    public string ActiveTheirsText => ActiveFile?.TheirsText ?? "";
+    public string ActiveResultText => ActiveFile?.ResultText ?? "";
+
     public bool HasCurrent => Current is not null;
     public int TotalConflicts => _flat.Count;
     public int ResolvedCount => _flat.Count(x => x.Block.IsResolved);
     public string? CurrentPath => InRange ? _flat[CurrentIndex].File.Path : null;
 
-    public string PositionText => _flat.Count == 0
-        ? "No text conflicts"
-        : $"Conflict {CurrentIndex + 1} of {_flat.Count}  ·  {ResolvedCount} resolved";
+    public string PositionText
+    {
+        get
+        {
+            if (ActiveFile is null || ActiveFile.Conflicts.Count == 0) return "No text conflicts";
+            var count = ActiveFile.Conflicts.Count;
+            var resolved = ActiveFile.Conflicts.Count(c => c.IsResolved);
+            return $"{count} conflicts · {resolved} resolved";
+        }
+    }
 
     public IReadOnlyList<string> BinaryFilePaths => Files.Where(f => f.IsBinary).Select(f => f.Path).ToList();
     public bool HasBinaryFiles => Files.Any(f => f.IsBinary);
@@ -66,6 +98,7 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     {
         _worker = worker;
         _taskId = taskId;
+        _conflictTaskId = taskId;
     }
 
     /// <summary>Starts the conflict merge and loads the conflicted files as line-level segments.
@@ -83,26 +116,7 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
                     Error = start.ErrorMessage;
                 return false;
             }
-
-            var docs = await _worker.GetMergeConflictDocumentsAsync(_taskId);
-            Files.Clear();
-            _flat.Clear();
-            foreach (var f in docs.Files)
-            {
-                var segments = f.Segments.Select(s => s.IsConflict
-                    ? MergeFileSegment.FromConflict(Hook(new MergeConflictBlock(s.Ours, s.Base, s.Theirs)))
-                    : MergeFileSegment.Stable(s.Text)).ToList();
-                var file = new MergeFile(f.Path, f.IsBinary, segments);
-                Files.Add(file);
-                foreach (var c in file.Conflicts) _flat.Add((file, c));
-            }
-
-            OnPropertyChanged(nameof(TotalConflicts));
-            OnPropertyChanged(nameof(BinaryFilePaths));
-            OnPropertyChanged(nameof(HasBinaryFiles));
-            RecomputeCanContinue();
-            if (_flat.Count > 0) MoveTo(0);
-            return Files.Count > 0;
+            return await LoadDocumentsAsync();
         }
         catch (Exception ex)
         {
@@ -112,6 +126,53 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
         finally { IsBusy = false; }
     }
 
+    /// <summary>Resolves a planning unit-merge conflict for <paramref name="subtaskId"/>. The merge is
+    /// already mid-conflict (driven by the orchestrator), so this only loads the conflicted files;
+    /// continue/abort hand back to the orchestrator on <paramref name="planningParentId"/>.</summary>
+    public async Task<bool> OpenForPlanningAsync(string planningParentId, string subtaskId)
+    {
+        _planningParentId = planningParentId;
+        _conflictTaskId = subtaskId;
+        IsBusy = true;
+        Error = null;
+        try
+        {
+            return await LoadDocumentsAsync();
+        }
+        catch (Exception ex)
+        {
+            Error = ex.Message;
+            return false;
+        }
+        finally { IsBusy = false; }
+    }
+
+    private async Task<bool> LoadDocumentsAsync()
+    {
+        var docs = await _worker.GetMergeConflictDocumentsAsync(_conflictTaskId);
+        Files.Clear();
+        _flat.Clear();
+        foreach (var f in docs.Files)
+        {
+            var segments = f.Segments.Select(s => s.IsConflict
+                ? MergeFileSegment.FromConflict(Hook(new MergeConflictBlock(s.Ours, s.Base, s.Theirs)))
+                : MergeFileSegment.Stable(s.Text)).ToList();
+            var file = new MergeFile(f.Path, f.IsBinary, segments);
+            Files.Add(file);
+            foreach (var c in file.Conflicts) _flat.Add((file, c));
+        }
+
+        OnPropertyChanged(nameof(TotalConflicts));
+        OnPropertyChanged(nameof(BinaryFilePaths));
+        OnPropertyChanged(nameof(HasBinaryFiles));
+        RecomputeCanContinue();
+        if (_flat.Count > 0)
+            MoveTo(0); // also sets ActiveFile via MoveTo
+        else if (Files.Count > 0)
+            ActiveFile = Files[0];
+        return Files.Count > 0;
+    }
+
     private MergeConflictBlock Hook(MergeConflictBlock block)
     {
         block.PropertyChanged += OnBlockChanged;
@@ -125,6 +186,7 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
             RecomputeCanContinue();
             OnPropertyChanged(nameof(ResolvedCount));
             OnPropertyChanged(nameof(PositionText));
+            OnPropertyChanged(nameof(ActiveResultText));
         }
     }
 
@@ -135,10 +197,22 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     {
         CurrentIndex = index;
         Current = _flat[index].Block;
+        ActiveFile = _flat[index].File;
         OnPropertyChanged(nameof(CurrentPath));
         CurrentChanged?.Invoke();
     }
 
+    [RelayCommand]
+    private void SelectFile(MergeFile file)
+    {
+        // Jump to the first conflict in this file (if any); otherwise just switch the active file.
+        var idx = _flat.FindIndex(x => x.File == file);
+        if (idx >= 0)
+            MoveTo(idx);
+        else
+            ActiveFile = file;
+    }
+
     private bool CanGoNext() => CurrentIndex >= 0 && CurrentIndex < _flat.Count - 1;
     private bool CanGoPrevious() => CurrentIndex > 0;
 
@@ -157,7 +231,16 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
         try
         {
             foreach (var file in Files.Where(f => !f.IsBinary))
-                await _worker.WriteConflictResolutionAsync(_taskId, file.Path, file.Compose());
+                await _worker.WriteConflictResolutionAsync(_conflictTaskId, file.Path, file.Compose());
+
+            if (_planningParentId is not null)
+            {
+                // Hand back to the orchestrator: it commits this subtask and drains the rest.
+                // A later subtask conflict re-opens this editor via the PlanningMergeConflict broadcast.
+                await _worker.ContinuePlanningMergeAsync(_planningParentId);
+                CloseRequested?.Invoke();
+                return;
+            }
 
             var result = await _worker.ContinueConflictMergeAsync(_taskId);
             if (string.Equals(result.Status, "merged", StringComparison.Ordinal))
@@ -176,7 +259,13 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     private async Task AbortAsync()
     {
         IsBusy = true;
-        try { await _worker.AbortConflictMergeAsync(_taskId); }
+        try
+        {
+            if (_planningParentId is not null)
+                await _worker.AbortPlanningMergeAsync(_planningParentId);
+            else
+                await _worker.AbortConflictMergeAsync(_taskId);
+        }
         catch (Exception ex) { Error = ex.Message; }
         finally
         {

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -41,9 +41,6 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
 
     public Func<MergeModalViewModel> ResolveMergeVm => _mergeVmFactory;
 
-    // Set by MainWindow to open the conflict resolution dialog.
-    public Func<ConflictResolutionViewModel, Task>? ShowConflictDialog { get; set; }
-
     // Layer C seam: composition root sets the factory; MainWindow sets the dialog opener.
     // The integrator connects Layer A/B's RequestConflictResolution(taskId, target) to this method.
     public Func<string, ClaudeDo.Ui.ViewModels.Conflicts.ConflictResolverViewModel>? ConflictResolverFactory { get; set; }
@@ -146,44 +143,17 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     private void OnPlanningMergeConflict(string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles)
     {
         // Already on UI thread (WorkerClient dispatches via Dispatcher.UIThread.Post).
-        _ = OpenConflictDialogAsync(planningTaskId, subtaskId, conflictedFiles);
+        // A unit-merge conflict resolves in the same in-app 3-way editor as a single-task merge.
+        _ = OpenPlanningConflictAsync(planningTaskId, subtaskId);
     }
 
-    private async Task OpenConflictDialogAsync(string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles)
+    private async Task OpenPlanningConflictAsync(string planningTaskId, string subtaskId)
     {
-        if (ShowConflictDialog == null || _dbFactory == null) return;
-
-        string subtaskTitle = subtaskId;
-        // The conflict lives in the list's working dir (the repo being merged into),
-        // not the subtask worktree. VS Code must open this folder to show the merge UI.
-        string repoDirectory = System.Environment.CurrentDirectory;
-        string targetBranch = Worker?.LastApproveTarget ?? "main";
-
-        try
-        {
-            await using var ctx = await _dbFactory.CreateDbContextAsync();
-            var entity = await ctx.Tasks
-                .Include(t => t.List)
-                .AsNoTracking()
-                .FirstOrDefaultAsync(t => t.Id == subtaskId);
-            if (entity != null)
-            {
-                subtaskTitle = entity.Title;
-                if (entity.List?.WorkingDir is { } dir && !string.IsNullOrWhiteSpace(dir))
-                    repoDirectory = dir;
-            }
-        }
-        catch { /* Non-fatal: fall back to subtaskId and cwd */ }
-
-        var vm = new ConflictResolutionViewModel(
-            Worker!,
-            planningTaskId,
-            subtaskTitle,
-            targetBranch,
-            conflictedFiles,
-            repoDirectory);
-
-        await ShowConflictDialog(vm);
+        if (ConflictResolverFactory is null || ShowConflictResolver is null) return;
+        var vm = ConflictResolverFactory(subtaskId);
+        var hasConflicts = await vm.OpenForPlanningAsync(planningTaskId, subtaskId);
+        if (hasConflicts)
+            await ShowConflictResolver(vm);
     }
 
     // For tests only — does NOT wire up events.

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

@@ -1,90 +0,0 @@
-using System.Diagnostics;
-using CommunityToolkit.Mvvm.ComponentModel;
-using CommunityToolkit.Mvvm.Input;
-using ClaudeDo.Ui.Localization;
-using ClaudeDo.Ui.Services;
-
-namespace ClaudeDo.Ui.ViewModels.Planning;
-
-public sealed partial class ConflictResolutionViewModel : ObservableObject
-{
-    private readonly IWorkerClient _worker;
-    private readonly string _planningTaskId;
-    // The repository directory that is currently mid-merge (the list's working dir),
-    // NOT the subtask worktree. Opening this folder is what makes VS Code show its
-    // merge-conflict resolution UI.
-    private readonly string _repoDirectory;
-
-    public string SubtaskTitle { get; }
-    public string TargetBranch { get; }
-    public IReadOnlyList<string> ConflictedFiles { get; }
-    public string SubtaskLabel => Loc.T("vm.conflictResolution.subtaskPrefix", SubtaskTitle);
-    public string TargetLabel  => Loc.T("vm.conflictResolution.targetPrefix", TargetBranch);
-
-    [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 repoDirectory)
-    {
-        _worker = worker;
-        _planningTaskId = planningTaskId;
-        _repoDirectory = repoDirectory;
-        SubtaskTitle = subtaskTitle;
-        TargetBranch = targetBranch;
-        ConflictedFiles = conflictedFiles;
-    }
-
-    [RelayCommand]
-    private void OpenInVsCode()
-    {
-        try
-        {
-            // Open the folder that is mid-merge so VS Code shows the Source Control
-            // merge-conflict UI for every conflicted file. Opening individual files
-            // gives only a plain editor with no conflict resolution affordances.
-            Process.Start(new ProcessStartInfo
-            {
-                FileName = "code",
-                Arguments = $"\"{_repoDirectory}\"",
-                UseShellExecute = true,
-            });
-            VsCodeError = null;
-        }
-        catch (Exception ex)
-        {
-            VsCodeError = Loc.T("vm.conflictResolution.vsCodeError", ex.Message);
-        }
-    }
-
-    [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; }
-    }
-}