[Vivswan]

What this changes

summaryTableProblems: a first-pipe-block table finder, a backslash-run pipe counter, a delimiter-row regex
  ->  fromMarkdown + gfmTable, the first table node, each row's cell count against the header's

differential, old against new, verdict and problem kind:
  700 summaries through the engine's own renderers, hostile cells (pipes, backslashes, code spans, <br>)   0 mismatches
  262 real summaries from fuzz scenarios and the curated corpus                                             0 mismatches
  75 malformed inputs + 10,501 mutations: every split is a shape the engine cannot write

How

• A malformed delimiter row now reads as no table, which is what GFM and GitHub's renderer make of it; the old finder named the separator row.
• mdast keeps a row's excess cells where the HTML renderer drops them, so a raw pipe shows as four cells under a three-cell header; the check stands on that.
• Library: the mdast GFM table stack already declared and used by .github/scripts/lib/generated-regions.ts.

Proof

• Tests: fuzz 9 pass; e2e 373/373; a ten-iteration fuzz run.
• Gates: typecheck, fleet biome 0, member-shape 0, knip, line cap.

Technical details

• Wording of three fuzz diagnostics moved: the missing-table message covers a malformed delimiter row, the rows message counts data rows, the cells message numbers the data row.
• Out of scope: shapes the engine cannot write (an indented table, a row without its leading or closing pipe, text glued to the table, a destroyed first table in a multi-target summary).
• No unit test: fuzz.ts runs main() at import, so its functions cannot be imported; a follow-up could guard it with import.meta.main and pin the excess-cell fact.
• Files: test/e2e/fuzz.ts.

[github-actions]

File size check

0 over a hard cap (fails), 6 warning(s).

File	Size	Tier	Cap
src/engine/diff.ts:56	11 comment lines	warn	10
src/github/api-error.ts:9	11 comment lines	warn	10
src/problem.ts:73	18 comment lines	warn	10
src/sections/contract/errors.ts:13	11 comment lines	warn	10
src/sections/contract/module.ts:55	12 comment lines	warn	10
src/sections/shared/list/decl.ts:265	14 comment lines	warn	10

Split the file, wrap the line, shorten or exempt the comment, or list the path in .file-size-allow.local with a # reason.

5 managed file(s) skipped; repo-platform owns them.

[Copilot]

🟢 Approval recommended

The focused test-only refactor preserves the intended validation checks, with no unresolved defects identified.

No open issues 🎉

What changed in this PR

Replaces the end-to-end fuzzer's custom Markdown table parser with the existing mdast GFM table stack, aligning summary validation with GFM parsing.

Changes:

• Parses the first table and checks its data-row count and cell widths against expectations.
• Updates diagnostics for missing tables, insufficient rows, and mismatched cell counts.

File	Description
test/​e2e/​fuzz.ts	Uses mdast GFM parsing for summary-table validation and updates diagnostics.

_{Review effort: Balanced}