feat(feishu): auto-convert markdown tables to native table component

[UniGood]

Problem

Feishu's post-type md elements cannot render markdown tables. When the adapter detects a table in outbound content, it falls back to plain text — the user sees raw pipe characters like | Name | Age | instead of a proper table.

Solution

Intercept markdown tables in _build_outbound_payload() and convert them to Feishu card v2 interactive cards using the native table component. The card renders tables as proper interactive tables with columns, rows, and pagination.

No LLM involved — pure regex detection + string parsing, zero additional latency.

Changes

gateway/platforms/feishu.py

• _build_table_card_payload(content) — Parses markdown table content and builds a Feishu card v2 JSON with native table component. Returns None on failure (caller falls back to plain text).
• _build_feishu_table_element(seg) — Builds a Feishu card v2 table component dict from a parsed table segment (columns + rows).
• _parse_table_segments(content) — Splits content into alternating text/table segments. Tables are parsed into header + rows dicts.
• _TABLE_MAX_ROWS = 50 — Truncation threshold; large tables get a warning note.
• Modified _build_outbound_payload() — Tries card conversion first when table detected; falls back to plain text on failure.

tests/gateway/test_feishu.py

• 11 tests in TestBuildTableCardPayload covering:
  • Single table → card with native table component
  • Mixed text + table
  • Multiple tables in one message
  • Large table truncation (>50 rows)
  • Malformed input handling
  • Empty/whitespace input
  • Alignment markers stripped
  • Integration with _build_outbound_payload()

Behavior

• Message with table: Before = Plain text (raw pipes), After = Card v2 with native table component
• Mixed text + table: Before = Plain text, After = Card with markdown text + table elements
• Table 50+ rows: Before = Plain text (full), After = Card (truncated + warning)
• Parse failure: Before = Plain text, After = Plain text (unchanged fallback)

Testing

All 216 tests pass: python -m pytest tests/gateway/test_feishu.py -x -q