fix(feishu): use post(md) for messages containing markdown tables

[liuhao1024]

What does this PR do?

Removes the outdated _MARKDOWN_TABLE_RE guard that forced table-containing Feishu messages to plain text type. Feishu's post(md) element now supports GFM tables (CommonMark 0.31 + GFM), so the workaround is no longer needed and actively harms message quality — it strips all formatting (bold, lists, code blocks) and renders tables as raw pipe characters.

Table detection is merged into _MARKDOWN_HINT_RE so tables trigger post(md) mode like other markdown features.

Related Issue

Fixes #58269

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• plugins/platforms/feishu/adapter.py: Removed _MARKDOWN_TABLE_RE regex and its guard in _build_outbound_payload() that forced text type for table content. Added table pattern ^\|.*\|\n\|[-|: ]+\| to _MARKDOWN_HINT_RE so tables trigger post(md) mode.
• tests/gateway/test_feishu.py: Added test_send_uses_post_for_markdown_table to verify table content is sent as post type with md tag.

How to Test

1. Run pytest tests/gateway/test_feishu.py::TestAdapterBehavior::test_send_uses_post_for_markdown_table -xvs — should pass.
2. Run pytest tests/gateway/test_feishu.py -q — all 206 tests should pass.
3. On a live Feishu bot, send a message containing a markdown table (e.g. | Col A | Col B |\n|---|---|\n| 1 | 2 |). Observed result: the table renders with grid lines and other markdown (bold, lists) is preserved.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes
• I've tested on my platform: macOS 15.4

Documentation & Housekeeping

• I've updated relevant documentation — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A

[teknium1]

Thanks for tracing this to the table-specific fallback. The premise remains present on current main: plugins/platforms/feishu/adapter.py:4528-4538 sends the reported pipe-bounded table shape as text, and Feishu’s current message-content documentation supports GFM through post/md.

Problems

• The new alternative at plugins/platforms/feishu/adapter.py:155 requires both the header and separator row to begin with |. GFM allows outer pipes to be omitted, so A | B\n--- | ---\n1 | 2 still misses _MARKDOWN_HINT_RE and takes the text fallback at plugins/platforms/feishu/adapter.py:4535-4538.

Suggested changes

• Make the outer pipes optional in the table detector and add a regression test for that valid GFM form, asserting post plus an md element.

Automated hermes-sweeper review.

[teknium1]

This requires outer pipes on both header and delimiter rows, but GFM permits them to be omitted. Please recognize A | B\n--- | ---\n1 | 2 as well and add a matching send-payload regression test; otherwise that valid table still falls through to text.

[teknium1]

Closing — this was fixed on main by #68121, which removes the _MARKDOWN_TABLE_RE force-text downgrade and routes tables through post/md, the same direction as this PR. Your updated plugin-path version of #38834 — same mechanism as the landed fix. The salvage was based on #58019 (cleanest implementation vs current main, with tests) with #29552 credited as the earliest submitter against the live plugin adapter path; both authors' commits were cherry-picked with authorship preserved. Thanks for contributing a fix for this — it was one of the most-reported bugs in the tracker.