fix(feishu): stop downgrading messages with tables to plain text

[BravianZhao]

Summary

FeishuAdapter._build_outbound_payload force-routes any message containing a markdown table to msg_type=text to avoid an old blank-message bug. Side-effect: every other markdown feature in the same reply -- headings, bold, fenced code, inline code, links, lists -- also gets stripped, because the whole message becomes plain text.

A research summary that happens to include one comparison table comes out as a wall of raw **bold**, `code`, ## heading and |---| characters.

Root cause

The protective table-downgrade dates back to a real client bug, but Feishu's post-type md element renders markdown tables natively on lark-oapi 1.5.x + Feishu/Lark client V7+. The downgrade is now pessimistic: it punishes every non-table markdown element in the message to guard against a problem that no longer exists.

Fix

Route any markdown content (tables included) through the existing _build_markdown_post_payload pipeline. _build_markdown_post_rows already splits on fenced code, so tables now coexist with prose, code, links, and emoji in a single message.

-        if _MARKDOWN_TABLE_RE.search(content):
-            text_payload = {"text": content}
-            return "text", json.dumps(text_payload, ensure_ascii=False)
-        if _MARKDOWN_HINT_RE.search(content):
+        if _MARKDOWN_HINT_RE.search(content) or _MARKDOWN_TABLE_RE.search(content):
             return "post", _build_markdown_post_payload(content)

_MARKDOWN_TABLE_RE is kept (as a hint that table-only content is still markdown) so a bare table without any other markdown still flows through post instead of falling to plain text.

Verification

Verified on Feishu desktop (China region, Lark domain) with lark-oapi 1.5.3 by sending the same composite reply twice -- once as text, once as post:

• Composite content: two markdown tables (right-aligned numerics, emoji), a fenced Python code block, ## headings, **bold**, bulleted list, inline `code`, and a [link](https://...).
• msg_type=text (old behaviour): everything renders as literal markdown characters.
• msg_type=post (new behaviour): every feature including both tables renders natively.

Tests added in tests/gateway/test_feishu.py::TestOutboundPayloadRouting:

Test	Input	Expected
test_plain_text_uses_text_msg_type	"hello world"	text
test_plain_markdown_uses_post_msg_type	**bold** + link	post
test_markdown_table_alone_uses_post_msg_type	bare 2x2 table	post (regression)
test_markdown_table_with_surrounding_content_keeps_post	heading + bold + table + code	post (regression)

All 4 pass on Python 3.11.15:

tests/gateway/test_feishu.py::TestOutboundPayloadRouting::test_markdown_table_alone_uses_post_msg_type PASSED
tests/gateway/test_feishu.py::TestOutboundPayloadRouting::test_markdown_table_with_surrounding_content_keeps_post PASSED
tests/gateway/test_feishu.py::TestOutboundPayloadRouting::test_plain_markdown_uses_post_msg_type PASSED
tests/gateway/test_feishu.py::TestOutboundPayloadRouting::test_plain_text_uses_text_msg_type PASSED
======================== 4 passed in 11.18s ========================

Rollback

Single-file fix in plugins/platforms/feishu/adapter.py. Revert the commit to restore the previous downgrade behaviour if a regression on an older Feishu client is reported.

Risk

Low. The post path was already in use for every other markdown message; this PR only widens the input set it accepts. If an old client without table support exists in the wild, the table cells fall through as plain text inside an otherwise correctly rendered post message -- strictly better than today's outcome where the entire message degrades to raw markdown.

[alt-glitch]

This was generated by AI during triage.

Duplicate of #52790 — same minimal mechanism (stop force-downgrading table-bearing markdown to msg_type=text; route it through the existing post+md payload path in plugins/platforms/feishu/adapter.py) and same file. #52790 is the earlier open twin for this exact approach. Related to the broader Feishu-table cluster (#52046 issue; native-Card-table approaches #46727/#37728; aggressive rewrite #28030; #27922). A human should pick one PR from the cluster.