feat(ui): merge action and robust jump-to-task in worktrees overview

Add Merge entry to the worktrees overview context menu wiring the existing
MergeModalViewModel, replace fire-and-forget list selection with a
collection-change-aware JumpToTaskHelper, and propagate list renames to
visible task rows via a new ListUpdated event.

Harden worktree state changes: WorkerHub.SetWorktreeState now rejects
invalid transitions, WorktreeMaintenanceService only drops the DB row when
the on-disk worktree was actually removed, and Cleanup/Reset broadcast
WorktreeUpdated for affected tasks. SetWorktreeStateAsync returns the hub
error message so the modal can surface it.

Also: de-duplicate the worktrees overview modal opener, hook
OnParentTaskIdChanged to refresh IsDraft, fix MergeModal CanExecute
notifications, and add WorktreeStateHubTests for the transition rules.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Worker/Worktrees/WorktreeMaintenanceService.cs

@@ -7,8 +7,8 @@ namespace ClaudeDo.Worker.Worktrees;
 
 public sealed class WorktreeMaintenanceService
 {
-    public sealed record CleanupResult(int Removed);
-    public sealed record ResetResult(int Removed, int TasksAffected, bool Blocked, int RunningTasks);
+    public sealed record CleanupResult(int Removed, IReadOnlyList<string> RemovedTaskIds);
+    public sealed record ResetResult(int Removed, int TasksAffected, bool Blocked, int RunningTasks, IReadOnlyList<string> RemovedTaskIds);
     public sealed record ForceRemoveResult(bool Removed, string? Reason);
 
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
@@ -40,12 +40,16 @@ public sealed class WorktreeMaintenanceService
         var rows = await query.AsNoTracking().Select(x => x.Row).ToListAsync(ct);
 
         int removed = 0;
+        var removedTaskIds = new List<string>();
         foreach (var row in rows)
         {
             if (await TryRemoveAsync(row, force: false, ct))
+            {
                 removed++;
+                removedTaskIds.Add(row.TaskId);
+            }
         }
-        return new CleanupResult(removed);
+        return new CleanupResult(removed, removedTaskIds);
     }
 
     public async Task<ResetResult> ResetAllAsync(CancellationToken ct = default)
@@ -54,7 +58,7 @@ public sealed class WorktreeMaintenanceService
         var running = await context.Tasks.AsNoTracking()
             .CountAsync(t => t.Status == ClaudeDo.Data.Models.TaskStatus.Running, ct);
         if (running > 0)
-            return new ResetResult(0, 0, Blocked: true, RunningTasks: running);
+            return new ResetResult(0, 0, Blocked: true, RunningTasks: running, Array.Empty<string>());
 
         var rows = await (from w in context.Worktrees
                           join t in context.Tasks on w.TaskId equals t.Id
@@ -64,12 +68,16 @@ public sealed class WorktreeMaintenanceService
                          .ToListAsync(ct);
 
         int removed = 0;
+        var removedTaskIds = new List<string>();
         foreach (var row in rows)
         {
             if (await TryRemoveAsync(row, force: true, ct))
+            {
                 removed++;
+                removedTaskIds.Add(row.TaskId);
+            }
         }
-        return new ResetResult(removed, rows.Count, Blocked: false, RunningTasks: 0);
+        return new ResetResult(removed, rows.Count, Blocked: false, RunningTasks: 0, removedTaskIds);
     }
 
     public async Task<IReadOnlyList<WorktreeOverviewRow>> GetOverviewAsync(
@@ -122,9 +130,11 @@ public sealed class WorktreeMaintenanceService
     private async Task<bool> TryRemoveAsync(WorktreeRow row, bool force, CancellationToken ct)
     {
         var repoDirExists = !string.IsNullOrWhiteSpace(row.WorkingDir) && Directory.Exists(row.WorkingDir);
+        bool dirRemoved;
 
         if (repoDirExists)
         {
+            dirRemoved = true;
             try
             {
                 await _git.WorktreeRemoveAsync(row.WorkingDir!, row.Path, force, ct);
@@ -137,15 +147,19 @@ public sealed class WorktreeMaintenanceService
                 catch (Exception delEx)
                 {
                     _logger.LogError(delEx, "Directory.Delete fallback also failed for {Path}", row.Path);
+                    dirRemoved = false;
                 }
             }
+            if (Directory.Exists(row.Path)) dirRemoved = false;
         }
         else
         {
+            dirRemoved = true;
             try { if (Directory.Exists(row.Path)) Directory.Delete(row.Path, recursive: true); }
             catch (Exception ex)
             {
                 _logger.LogError(ex, "Directory.Delete failed for {Path}", row.Path);
+                dirRemoved = false;
             }
         }
 
@@ -170,6 +184,10 @@ public sealed class WorktreeMaintenanceService
             }
         }
 
+        // Drop the DB row only when the on-disk worktree is gone; otherwise we'd silently
+        // strand a directory while reporting success.
+        if (!dirRemoved) return false;
+
         using var context = _dbFactory.CreateDbContext();
         await context.Worktrees.Where(w => w.TaskId == row.TaskId).ExecuteDeleteAsync(ct);
         return true;