a11y: run axe over Holocene stories in CI (report-only)

[ardiewen]

Summary

Runs axe over every Holocene story (271) in CI, via the existing stories:test runner (@storybook/addon-a11y + axe-playwright). This catches the per-component structural / name / contrast band that the Svelte compiler gate (#3682) structurally cannot see — the biggest single coverage gain for shift-left a11y, since fixing a primitive cascades to every consumer.

Report-only for now (continue-on-error: true): the baseline isn't clean, so the job surfaces violations in the log without blocking merge. Remove continue-on-error to make it a hard gate once the baseline below is burned down.

Baseline to burn down — 13 failing tests / 6 components

• vertical-nav (6 stories) — aria-current, aria-required-parent/children, aria-disabled
• duration-input (2), deployments-compute-badge (2), code-block (With Header), markdown-editor, tab-button
• Top rules: aria-disabled (29), aria-required-parent/children (8 — often isolated-render artifacts, i.e. a child role rendered without its required parent in the story), aria-current (6), color-contrast (2), label, button-name.

Notes

• Uses pnpm dlx for the serve tooling (http-server / wait-on / concurrently) to avoid lockfile churn — vendor them as devDeps when flipping to blocking.
• Runs on every PR (~2–4 min: SB build + axe). Could move to a nightly schedule if per-PR cost is a concern.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
holocene	Ready	Preview, Comment	Jul 16, 2026 7:26pm

[github-actions]

Accessibility triage

No A11y-Audit-Ref: lines found in the PR body. If this PR closes an audit fix doc, add an A11y-Audit-Ref: <slug> line (one per fix doc). If this is a net-new accessibility finding not yet covered by the audit, coordinate with the audit team via #team-feux so they can add a manifest entry.

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_{See DT-4048 for the triage system design.}