feat(attachments): inject reference files into the run + clean up files on delete

TaskRunner appends attached files (absolute paths) to the run prompt as the
read-only Reference files section. Task and list deletes now remove the
on-disk attachment dir eagerly, and a startup AttachmentOrphanRecovery sweep
drops any attachments/<taskId>/ whose task no longer exists (covers list
cascade and planning-discard paths).

src/ClaudeDo.Worker/Runner/TaskRunner.cs

@@ -21,6 +21,7 @@ public sealed class TaskRunner
     private readonly ILogger<TaskRunner> _logger;
     private readonly ITaskStateService _state;
     private readonly TaskRunTokenRegistry _tokens;
+    private readonly AttachmentStore _attachments;
 
     public TaskRunner(
         IClaudeProcess claude,
@@ -31,7 +32,8 @@ public sealed class TaskRunner
         WorkerConfig cfg,
         ILogger<TaskRunner> logger,
         ITaskStateService state,
-        TaskRunTokenRegistry tokens)
+        TaskRunTokenRegistry tokens,
+        AttachmentStore attachments)
     {
         _claude = claude;
         _dbFactory = dbFactory;
@@ -42,6 +44,7 @@ public sealed class TaskRunner
         _logger = logger;
         _state = state;
         _tokens = tokens;
+        _attachments = attachments;
     }
 
     public async Task RunAsync(TaskEntity task, string slot, CancellationToken ct, bool alreadyClaimed = false)
@@ -54,6 +57,7 @@ public sealed class TaskRunner
             ListConfigEntity? listConfig;
             List<SubtaskEntity> subtasks;
 
+            List<string>? attachmentPaths = null;
             using (var context = _dbFactory.CreateDbContext())
             {
                 var listRepo = new ListRepository(context);
@@ -67,6 +71,11 @@ public sealed class TaskRunner
 
                 var subtaskRepo = new SubtaskRepository(context);
                 subtasks = await subtaskRepo.GetByTaskIdAsync(task.Id, ct);
+
+                var attachmentRepo = new TaskAttachmentRepository(context);
+                var attachments = await attachmentRepo.ListByTaskIdAsync(task.Id, ct);
+                if (attachments.Count > 0)
+                    attachmentPaths = attachments.Select(a => Path.Combine(_attachments.TaskDir(task.Id), a.FileName)).ToList();
             }
 
             // Determine working directory: worktree or sandbox.
@@ -114,7 +123,8 @@ public sealed class TaskRunner
             // Build prompt: title + description + only the OPEN sub-tasks (resolved ones are dropped).
             var prompt = TaskPromptComposer.Compose(
                 task.Title, task.Description,
-                subtasks.Select(s => (s.Title, s.Completed)));
+                subtasks.Select(s => (s.Title, s.Completed)),
+                attachmentPaths);
 
             // Run 1.
             var result = await RunOnceAsync(task.Id, task.Title, slot, runDir, resolvedConfig, 1, false, prompt, ct);