feat(worker): PlanningSessionManager.ResumeAsync

src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs

@@ -53,6 +53,25 @@ public sealed class PlanningSessionManager
         return new PlanningSessionStartContext(taskId, list.WorkingDir, files);
     }
 
+    public async Task<PlanningSessionResumeContext> ResumeAsync(string taskId, CancellationToken ct)
+    {
+        var task = await _tasks.GetByIdAsync(taskId, ct)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        if (task.Status != TaskStatus.Planning)
+            throw new InvalidOperationException($"Task is in status {task.Status}; resume requires Planning.");
+        if (string.IsNullOrEmpty(task.PlanningSessionId))
+            throw new InvalidOperationException("No Claude session ID captured yet; cannot resume.");
+
+        var sessionDir = Path.Combine(_rootDirectory, taskId);
+        var mcpConfigPath = Path.Combine(sessionDir, "mcp.json");
+        if (!File.Exists(mcpConfigPath))
+            throw new InvalidOperationException($"Session directory missing: {sessionDir}");
+
+        var list = await _lists.GetByIdAsync(task.ListId, ct)
+            ?? throw new InvalidOperationException($"List {task.ListId} not found.");
+        return new PlanningSessionResumeContext(taskId, list.WorkingDir, task.PlanningSessionId, mcpConfigPath);
+    }
+
     private static string GenerateToken()
     {
         var bytes = RandomNumberGenerator.GetBytes(32);