chore(compliance): lint universal-storyboard doc tables match filesystem

[bokelley]

Summary

Build-time + unit-test lint that prevents the drift #3099 just fixed from re-accumulating.

Stacked on #3099 (the doc refresh) so the lint sees an already-aligned tree. Once #3099 lands, this rebases to main automatically.

What it catches

• Forward parity: a new universal storyboard ships without a doc-table row → specific "missing rows for X" error.
• Reverse parity: a doc keeps a row for a renamed/deleted storyboard → "references X but no graded storyboard exists" error.
• Either index page loses its "Universal" heading → "missing expected heading" error.

How it works

• scripts/lint-universal-storyboard-doc-parity.cjs — new module exporting `lint({ sourceDir, repoRoot })` plus helpers, with a CLI entrypoint.
• scripts/build-compliance.cjs — calls lint inside `generateIndex`, so the compliance build fails loudly on drift.
• `tests/lint-universal-storyboard-doc-parity.test.cjs` — 10 tests: source-tree guard, clean fixture, non-graded fixtures filtered, forward parity (both docs), reverse parity (both docs), missing heading, helper unit tests.
• `package.json` — `test:storyboard-doc-parity` wired into the umbrella `test` target alongside other storyboard lints; CI picks it up automatically.

"Graded" = YAML has a `phases:` array. Filters out the three non-graded fixtures (`storyboard-schema.yaml`, `runner-output-contract.yaml`, `fictional-entities.yaml`) which live alongside graded storyboards.

The two docs use different slug conventions by design (existing convention, not changed):

• `conformance.mdx` uses snake_case YAML `id` values in markdown links
• `compliance-catalog.mdx` uses kebab-case filename slugs in plain backticks

Test plan

• `npm run test:storyboard-doc-parity` — 10/10 pass.
• `node scripts/build-compliance.cjs` — passes against current docs (post-docs(conformance, catalog): refresh universal-storyboards tables #3099 refresh).
• Sanity-checked drift detection: temporarily removed `webhook_emission` row → fired with clear error; injected ghost row → fired with reverse-parity error.
• TypeScript precommit hook — passes.

Why `--empty` changeset

Build-script + tests + new lint logic — no protocol-spec surface change. The lint encodes existing convention (the two index pages should agree with `static/compliance/source/universal/`), it doesn't introduce a new normative rule.

🤖 Generated with Claude Code

[bokelley]

Ran the lint by code-reviewer + dx-expert. Both said ship.

Code-reviewer: verified the regex/section-extraction edge cases hold up (trailing backtick anchors the slug capture; indexOf is fine for headings since a fenced ## Universal storyboards doesn't appear in either MDX); style matches existing scripts/lint-*.cjs neighbors; placement between verifyEnumParity and lintStoryboardIdempotency is correct ordering.

DX-expert: ship-with-nice-to-haves. Applied the two cheap ones in the follow-up commit:

1. Forward-parity error now says "using the {YAML id | filename slug} form" — parallels the reverse error and helps a contributor adding a new storyboard pick the right form without grepping existing rows.
2. JSX comment above each universal-storyboards table points at scripts/lint-universal-storyboard-doc-parity.cjs — discoverability for contributors editing the docs directly.

Skipped DX nice-to-have #3 (cross-form token detection — "oh, you put kebab-case in the snake-case doc") as more involved than the value justifies. The tokenLabel hint in the existing reverse-parity error already mitigates.

Tests still 10/10, build clean.