feat(feishu): stream updates on a single card (#1031)

* feat(feishu): stream updates on a single card

* fix(feishu): ensure final message on stream error and warn on missing card ID

- Wrap streaming loop in try/except/finally so a is_final=True outbound
  message is always published, even when the LangGraph stream breaks
  mid-way. This prevents _running_card_ids memory leaks and ensures the
  Feishu card shows a DONE reaction instead of hanging on "Working on it".
- Log a warning when _ensure_running_card gets no message_id back from
  the Feishu reply API, making silent fallback to new-card behavior
  visible in logs.
- Add test_handle_feishu_stream_error_still_sends_final to cover the
  error path.
- Reformat service.py dict comprehension (ruff format, no logic change).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid blocking inbound on Feishu card creation

---------

Co-authored-by: songyaolun <songyaolun@bytedance.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/README.md

@@ -127,6 +127,12 @@ FastAPI application providing REST endpoints for frontend integration:
 | `GET /api/threads/{id}/uploads/list` | List uploaded files |
 | `GET /api/threads/{id}/artifacts/{path}` | Serve generated artifacts |
 
+### IM Channels
+
+The IM bridge supports Feishu, Slack, and Telegram. Slack and Telegram still use the final `runs.wait()` response path, while Feishu now streams through `runs.stream(["messages-tuple", "values"])` and updates a single in-thread card in place.
+
+For Feishu card updates, DeerFlow stores the running card's `message_id` per inbound message and patches that same card until the run finishes, preserving the existing `OK` / `DONE` reaction flow.
+
 ---
 
 ## Quick Start