feat(harness): enforce prop default docs

[egdev6]

Summary

• Adds a verifier that fails when public component props with runtime defaults lack matching @default JSDoc in types.ts.
• Wires the verifier into local hooks and CI workflows.
• Updates contributor/auditor harness docs and existing component prop metadata so the new gate passes.

Closes #247

Review scope

• Primary files/areas:
  • scripts/verify-prop-default-docs.mjs
  • .atl/skills/** component contributor/auditor contract updates
  • .github/workflows/test.yml
  • .github/workflows/storybook-build.yml
  • lefthook.yml
  • component types.ts JSDoc metadata updates
• Out of scope:
  • Runtime component behavior changes.
  • Discord notification workflow.
  • Unrelated local working-tree files in the original checkout.
• Review workload: medium — many files, but most are docs/metadata and one verifier script.

Type of change

• New component
• Existing component update/refactor
• Bug fix
• Accessibility
• Design tokens
• Storybook/docs
• Infrastructure/tooling
• NPM/dependencies

Workflow gates

• Linked issue is present with Closes #NNN or maintainer approved an exception.
• Linked issue has label status:approved before implementation starts.
• Work was started through the Project flow: assignee set, Project status In progress, branch/worktree recorded.
• PR title follows Conventional Commit format: <type>(<optional scope>): <description>.
• Commits follow the same commitlint-enforced format.
• Diff is focused; unrelated work is called out in Review scope.
• MCP/runtime artifacts are absent: .playwright-mcp, page-*.png, page-*.jpeg, *.md.playwright-output.

Component evidence (required for component changes)

N/A — this PR changes component public prop documentation metadata only; no runtime component implementation changed.

Accessibility evidence

N/A — no runtime UI behavior changed.

Validation evidence

• TypeScript: pnpm exec tsc --noEmit passed via lefthook pre-commit.
• Unit tests: pnpm test passed via lefthook pre-push — 28 files, 440 tests.
• Build/package: N/A.
• Storybook or visual check: N/A — no visual/runtime changes.
• Accessibility check: N/A — no runtime UI changes.
• Security/dependency check: no dependency changes.
• Prop docs verifier: node scripts/verify-prop-default-docs.mjs passed.
• Formatting/lint: pnpm exec biome check <changed relevant files> passed via lefthook and manual validation.
• Workflow syntax: .github/workflows/test.yml and .github/workflows/storybook-build.yml parsed as YAML locally.
• Review: fresh-context reviewer found no blockers.

Screenshots or recordings

N/A — metadata/tooling change only.

Notes for reviewer

The verifier intentionally checks literal/defaultable cases and avoids broad semantic inference for complex derived values. It covers:

• hook/component destructuring defaults;
• empty array/object constants;
• CVA defaultVariants;
• nullish fallback chains such as disabled ?? isDisabled ?? false.