feat: 完成T-204b采集自动回写

采集完成且本轮有成功采集任务时，Tab① 自动启动 WriteBackWorker 回写旧标题和旧封面路径到当前批次 Excel。

保留手动回写旧数据到 Excel 作为自动回写失败后的重试入口；原 Excel 被占用时提示关闭文件后手动重试，SQLite 采集结果不回滚。

新增 GUI 测试覆盖自动触发、无成功采集不触发、锁文件提示手动重试；同步 T-204b 任务状态、current-state、api、architecture 与 progress。

app/gui.py

@@ -349,16 +349,34 @@ if QT_IMPORT_ERROR is None:
             if not batch_id:
                 self._set_status("没有可回写批次")
                 return
+            self._start_write_back(batch_id)
+
+        def _start_write_back(self, batch_id, auto=False):
+            if self.write_back_thread is not None:
+                self._set_status("Excel 回写正在进行...")
+                return False
             worker = WriteBackWorker(batch_id, db_path=self.db_path)
-            worker.failed.connect(self._on_write_back_failed)
-            worker.finished.connect(self._on_write_back_finished)
+            worker.failed.connect(
+                lambda task_id, error, auto=auto: self._on_write_back_failed(
+                    task_id,
+                    error,
+                    auto=auto,
+                )
+            )
+            worker.finished.connect(
+                lambda payload, auto=auto: self._on_write_back_finished(
+                    payload,
+                    auto=auto,
+                )
+            )
             thread = run_worker(worker, thread_name="WriteBackWorker", start=False)
             thread.finished.connect(lambda: self._forget_write_back_thread(thread))
             self.write_back_worker = worker
             self.write_back_thread = thread
             self._set_write_back_running(True)
-            self._set_status("正在回写旧数据到 Excel...")
+            self._set_status("正在自动回写旧数据到 Excel..." if auto else "正在回写旧数据到 Excel...")
             thread.start()
+            return True
 
         def _active_batch_id(self):
             if self.current_batch_id:
@@ -415,13 +433,22 @@ if QT_IMPORT_ERROR is None:
         def _on_collect_finished(self, payload):
             self._set_collect_running(False)
             self.refresh_tasks()
-            self._set_status(
-                "采集完成：成功{collected}，略过{skipped}，失败{failed}".format(
-                    collected=payload.get("collected", 0),
-                    skipped=payload.get("skipped", 0),
-                    failed=payload.get("failed", 0),
-                )
+            message = "采集完成：成功{collected}，略过{skipped}，失败{failed}".format(
+                collected=payload.get("collected", 0),
+                skipped=payload.get("skipped", 0),
+                failed=payload.get("failed", 0),
             )
+            if payload.get("collected", 0) > 0:
+                batch_id = self._active_batch_id()
+                if batch_id and self._start_write_back(batch_id, auto=True):
+                    self._set_status(f"{message}，正在自动回写 Excel...")
+                    return
+                if not batch_id:
+                    self._set_status(f"{message}，但没有可回写批次")
+                    return
+                self._set_status(f"{message}，Excel 回写已在进行")
+                return
+            self._set_status(message)
 
         def _on_collect_cancelled(self, payload):
             self._set_collect_running(False)
@@ -433,22 +460,27 @@ if QT_IMPORT_ERROR is None:
                 )
             )
 
-        def _on_write_back_failed(self, task_id, error):
-            message = f"Excel 回写失败：{error}"
+        def _on_write_back_failed(self, task_id, error, auto=False):
+            message = f"Excel {'自动' if auto else ''}回写失败：{error}"
             if "被占用" in str(error):
-                message += "\n请关闭原 Excel 后重试；SQLite 已保留采集结果，也可另存副本。"
+                if auto:
+                    message += "\n请关闭原 Excel 后点击「回写旧数据到 Excel」手动重试；SQLite 已保留采集结果，也可另存副本。"
+                else:
+                    message += "\n请关闭原 Excel 后重试；SQLite 已保留采集结果，也可另存副本。"
             QMessageBox.warning(self, "回写旧数据", message)
             self._set_status(message.replace("\n", " "))
 
-        def _on_write_back_finished(self, payload):
+        def _on_write_back_finished(self, payload, auto=False):
             self._set_write_back_running(False)
             if payload.get("ok") is False:
                 error = payload.get("error") or "未知错误"
-                self._set_status(f"Excel 回写失败：{error}")
+                retry_hint = "，可点击「回写旧数据到 Excel」手动重试" if auto else ""
+                self._set_status(f"Excel {'自动' if auto else ''}回写失败：{error}{retry_hint}")
                 return
             self.refresh_tasks()
             self._set_status(
-                "Excel 回写完成：文件{files}，行{rows}".format(
+                "Excel {prefix}回写完成：文件{files}，行{rows}".format(
+                    prefix="自动" if auto else "",
                     files=payload.get("files", 0),
                     rows=payload.get("rows", 0),
                 )