`_render_text_element` ran every inbound post text element through
`_escape_markdown_text`, so a user's `` `print('hi')` `` reached the model as
`` \`print\('hi'\)\` ``. The agent echoed those backslashes in its reply and
Feishu's `md` renderer then showed literal `\*\*bold\*\*` instead of bold.
Post elements carry raw text plus separate style flags; the style wrappers
already rebuild the markdown, so the text itself is passed through untouched.
The outbound path never escaped. Mentions/emoji labels keep their escaping.
Salvage of PR #9991 by @nightq onto `plugins/platforms/feishu/adapter.py`.
Fixes#9816
d131391ff9