Transplant of PR #26848 onto the plugin adapter path
(plugins/platforms/feishu/adapter.py — the original PR targeted the
since-removed gateway/platforms/feishu.py).
``send`` classifies each chunk independently, so chunk 1 of a long
markdown reply (often plain prose) went out as msg_type=text while
later chunks rendered as post — literal **bold**/## heading markers
in the Feishu client. Lock the decision at the whole-message level:
compute prefer_post once from the full formatted message and pass it
to _build_outbound_payload per chunk.
The original PR's per-chunk table exemption is intentionally dropped:
tables now route through post/md (issue #52786 cluster fix), so the
exemption would reintroduce the raw-table downgrade.
Co-authored-by: Hermes Agent <hermes@nousresearch.com>