- Add `reply_to_message: bool = False` config to `FeishuConfig`
- Parse `parent_id` and `root_id` from incoming events into metadata
- Fetch quoted message content via `im.v1.message.get` and prepend
`[Reply to: ...]` context for the LLM when a user quotes a message
- Add `_reply_message_sync` using `im.v1.message.reply` API so the
bot's response appears as a threaded quote in Feishu
- First outbound message uses reply API; subsequent chunks fall back
to `create` to avoid duplicate quote bubbles; progress messages
always use `create`
- Add 19 unit tests covering all new code paths
