fix(worker): 无 result_text_full 列的老库/手工表写回回落，不拖垮终局

CI 失败根因：P0 取消守卫测试 mock 掉 _ensure_result_columns
并手工建表（无新列），带新列的 UPDATE 直接
OperationalError。修法：带新列写回失败且错误含
result_text_full 时回滚并用旧 SQL 重写（摘要照写、完整版
丢弃），其它错误原样重抛。

cloud/worker.py

@@ -1467,37 +1467,56 @@ class Worker:
                 status_clause = " AND status = ?"
                 extra = (only_if_status,)
             full = (result_full[:200000] if result_full else None)
+            short = ((result_text or "")[:21000] if result_text else None)
+            err_short = ((error_text or "")[:4000]
+                         if error_text else None)
+            now = time.time()
             if child_pid is None:
-                cur = conn.execute(
+                sql_full = (
                     "UPDATE tasks SET result_text = ?,"
                     " result_text_full = ?, error_text = ?,"
                     " actual_model = ?, started_at = ?, finished_at = ?,"
                     " turn_id = COALESCE(?, turn_id),"
                     " root_turn_id = COALESCE(?, root_turn_id),"
-                    " updated_at = ? WHERE id = ?" + status_clause,
-                    ((result_text or "")[:21000] if result_text else None,
-                     full,
-                     (error_text or "")[:4000] if error_text else None,
-                     actual_model, started_at, finished_at,
-                     turn_id, root_turn_id,
-                     time.time(), task_id) + extra,
-                )
+                    " updated_at = ? WHERE id = ?" + status_clause)
+                params_full = (short, full, err_short, actual_model,
+                               started_at, finished_at, turn_id,
+                               root_turn_id, now, task_id) + extra
+                sql_old = sql_full.replace(
+                    " result_text_full = ?,", "")
+                params_old = (short, err_short, actual_model,
+                              started_at, finished_at, turn_id,
+                              root_turn_id, now, task_id) + extra
             else:
-                cur = conn.execute(
+                sql_full = (
                     "UPDATE tasks SET result_text = ?,"
                     " result_text_full = ?, error_text = ?,"
                     " actual_model = ?, started_at = ?, finished_at = ?,"
                     " child_pid = ?,"
                     " turn_id = COALESCE(?, turn_id),"
                     " root_turn_id = COALESCE(?, root_turn_id),"
-                    " updated_at = ? WHERE id = ?" + status_clause,
-                    ((result_text or "")[:21000] if result_text else None,
-                     full,
-                     (error_text or "")[:4000] if error_text else None,
-                     actual_model, started_at, finished_at, child_pid,
-                     turn_id, root_turn_id,
-                     time.time(), task_id) + extra,
-                )
+                    " updated_at = ? WHERE id = ?" + status_clause)
+                params_full = (short, full, err_short, actual_model,
+                               started_at, finished_at, child_pid,
+                               turn_id, root_turn_id, now, task_id) + extra
+                sql_old = sql_full.replace(
+                    " result_text_full = ?,", "")
+                params_old = (short, err_short, actual_model,
+                              started_at, finished_at, child_pid,
+                              turn_id, root_turn_id, now, task_id) + extra
+            try:
+                cur = conn.execute(sql_full, params_full)
+            except Exception as exc:
+                # 老库/被 mock 掉迁移的库没有 result_text_full 列：
+                # 完整版丢弃、摘要照写，绝不让新列拖垮终局写回
+                # （P0 取消守卫测试就是 mock 掉迁移的手工表）。
+                if "result_text_full" not in str(exc):
+                    raise
+                try:
+                    conn.rollback()
+                except Exception:
+                    pass
+                cur = conn.execute(sql_old, params_old)
             conn.commit()
             return cur.rowcount == 1
         finally: