feat(feishu): render markdown tables as Feishu interactive card table elements

[jefferyzhang963]

Summary

Convert markdown tables in outbound Feishu messages to interactive-card JSON 2.0 native table elements instead of falling back to plain text.

Problem

Feishu post-type md elements cannot render markdown tables — sending table content as post causes the message to appear blank on the client. The workaround was to force plain text for anything that looked like a markdown table (_MARKDOWN_TABLE_RE). This makes tables barely readable.

Solution

When _build_outbound_payload detects a markdown table, it now:

1. Splits the content into alternating text/table segments
2. Parses each table into headers + data rows
3. Builds a Feishu interactive card with:
   • markdown elements for surrounding prose
   • table elements (with lark_md data type) for each detected table
4. Falls back to plain text if the card exceeds Feishu 30KB size limits

The card uses wide_screen_mode: true and row_height: "low" for compact rendering.

Changes

gateway/platforms/feishu.py (+207 / -11)

• New functions (lines 608–770): _is_table_separator_row, _parse_table_row, _pad_row, _parse_markdown_table, _split_content_by_tables, _build_table_card_element, _build_interactive_table_card
• Modified _build_outbound_payload: table detection now returns ("interactive", card_json) instead of ("text", ...)
• Modified send(): added interactive-card failure fallback (exception + response check)
• Modified edit_message(): added interactive-card failure fallback

tests/gateway/test_feishu.py (+333)

• 18 new tests in TestFeishuMarkdownTableCard covering:
  • Row/separator/table parsing
  • Content splitting (text-only, table-only, mixed, multiple tables)
  • Card JSON generation (single table, table + surrounding text, no table)
  • _build_outbound_payload integration (returns interactive for table, post for non-table)
  • Full send() integration (interactive card sends, API error fallback, response failure fallback)
  • edit_message() integration

Verification

• ✅ All 216 tests pass (198 existing + 18 new)
• ✅ Zero regressions
• ✅ Backward compatible: no-table messages still use post/text routing

Screenshots

Before: plain text table → barely readable
After: native Feishu card table with proper column alignment, inline markdown rendering

[alt-glitch]

Duplicate of #12114 — this is the 10th+ competing PR for Feishu markdown table → interactive card rendering. See also #24249, #25453, #17006, #20152, #27046, #26429, #27328. The canonical PR is #12114.