feat(core)!: score require-datetime and doctype by their evidence

[oekazuma]

The two severity questions the Phase B-4 review left open, decided on the principle that a rule without evidence gets demoted and a rule without meaning gets deleted. Neither is meaningless — both detect a real defect — so both are demoted rather than removed.

Why each

• a11y/require-datetime has evidence, but not accessibility evidence. Its requirement is HTML conformance; there is no WCAG criterion about <time>. A screen reader reads "last Tuesday" exactly as a sighted reader does — what the element loses is its machine-readable value. warning claimed more than that.
• a11y/doctype's accessibility premise has no source at all. Quirks mode is documented as a layout difference, and WCAG 4.1.1 Parsing, which used to justify markup-validity checks, is obsolete and removed. The layout claim is sourced, so the rule stays — at the weight that claim supports.

This is the standard #428 set for the SEO category: severity tracks the strength of the evidence.

Exit-code consequences, measured

Per rule, on a fixture isolated with --rules, before and after. Both movements loosen a gate; nothing tightens.

rule	--fail-on critical (default)	--fail-on warning	--fail-on info
a11y/require-datetime	0 → 0	1 → 0	1 → 1
a11y/doctype	0 → 0	1 → 0	1 → 1

A project on the default gate is unaffected. A project on --fail-on warning whose only finding is one of these two goes red → green.

Score consequences, measured

• a11y::component: 46 → 42 points of severity weight. On this repo's own example app the a11y category reads 83 → 87 with no change in findings.
• a11y::project: 5 → 1, absorbed by the floor of 25 — but a project-scope finding is an absolute deduction, so a missing doctype now costs its category 1 point instead of 5.
• The widest pair is unchanged at 100, so the floor's info < warning ordering invariant is untouched.

One caveat worth recording, since it caught me mid-measurement: scoring a rule in isolation with --rules also shrinks the inventory to that one rule, so the headline numbers from such a run (80 → 96, 95 → 99) are not what a real project sees. The 83 → 87 above is the full-run figure.

Also updated

Both rule pages carry the reason for the demotion in both languages, so the weight is legible rather than arbitrary; the generated rule-index pages, the explain --list snapshots, and the translation ledger follow.

pnpm build, pnpm typecheck, pnpm test, pnpm lint, translate:check all clean.

Still open

Two smaller Priority 2 items remain: accepting the literal undefined for aria-* boolean/tristate values, where the ARIA spec and Svelte's own compiler disagree, and uppercase ARIA attribute names being invisible to the collector (a false negative).

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Reclassified a11y/doctype and a11y/require-datetime findings from warnings to informational notices.
  • Updated rule scoring and exit-code behavior to reflect the reduced severity.

• Documentation

  • Updated English and Japanese accessibility rule listings and explanations.
  • Clarified that these rules relate primarily to HTML conformance and layout considerations rather than direct accessibility impact.
  • Added release notes for the upcoming minor version.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 105898c2-753f-468d-a45d-16e1a8850bc4

📥 Commits

Reviewing files that changed from the base of the PR and between adf3283 and 4a5176b.

⛔ Files ignored due to path filters (1)

• packages/cli/test/__snapshots__/gunshi-explain-parity.test.ts.snap is excluded by !**/*.snap

📒 Files selected for processing (12)

• .changeset/olive-spies-jam.md
• docs/blume.translations.json
• docs/src/content/docs/ja/rules/a11y/doctype.md
• docs/src/content/docs/ja/rules/a11y/index.mdx
• docs/src/content/docs/ja/rules/a11y/require-datetime.md
• docs/src/content/docs/ja/rules/index.mdx
• docs/src/content/docs/rules/a11y/doctype.md
• docs/src/content/docs/rules/a11y/index.mdx
• docs/src/content/docs/rules/a11y/require-datetime.md
• docs/src/content/docs/rules/index.mdx
• packages/core/src/rules/a11y/doctype.ts
• packages/core/src/rules/a11y/require-datetime.ts

Included review availability: Your plan includes up to 1 review per rolling hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The PR demotes a11y/doctype and a11y/require-datetime from warning to info severity. It updates rule implementations, English and Japanese documentation, translation revisions, and release metadata.

Changes

Accessibility severity updates

Layer / File(s)	Summary
Rule severity implementation packages/core/src/rules/a11y/*.ts	Both rules now report info severity. Comments describe their HTML conformance and layout-related rationale.
Documentation and release alignment .changeset/*, docs/src/content/docs/rules/..., docs/src/content/docs/ja/rules/..., docs/blume.translations.json	Rule indexes and detail pages classify both rules as info rules. Japanese translation revisions and minor-release metadata are updated.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 4a517

This PR lowers the severities of two existing findings and updates their documentation and generated references; the reported validation checks are clean, so no actionable merge-blocking risk remains beyond normal checks and review.

Possibly related PRs

• oekazuma/svelte-vitals#319: Updates related rule documentation indexes and severities.
• oekazuma/svelte-vitals#511: Reviews the accessibility rule validity that informs these severity changes.
• oekazuma/svelte-vitals#517: Clarifies rationale for the a11y/doctype and a11y/require-datetime changes.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the two affected rules and the evidence-based scoring change, which matches the main purpose of the pull request.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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