Phase 17: GFM table header/delimiter column-count parity (v0.1.14)

[lidonggui]

Summary

• Tighten looksLikeTable so a GFM table opens only when the delimiter row’s cell count equals the header’s (micromark/GFM parity: leading/trailing pipes optional; empty edge cells from outer pipes ignored).
• Mismatched counts stay a paragraph; ragged body rows with matching header/delimiter still form a table (body absorption unchanged).
• Phase 14 paragraph-interrupt uses the same tightened look-ahead. Docs + bump to 0.1.14.

Test plan

• pnpm verify (typecheck + test + build) green locally
• New Phase 17 cases: delim < header / delim > header → paragraph; matching → table; ragged body → table; mismatched does not interrupt as table
• CI green (or merge after verify if no required checks, matching prior phases)