[feat] New agent: accessibility-auditor

[lugassawan]

Goal

An accessibility-auditor subagent audits frontend code for WCAG violations, ARIA misuse, and keyboard-trap risks — pairing with principle-accessibility (#84).

Motivation

The reviewer agent performs general code review. Accessibility requires domain-specific pattern recognition (implicit ARIA roles, focus trap conditions, contrast ratio evaluation) that general reviewers miss. A dedicated accessibility auditor brings the same depth as the security-auditor does for security, but for the a11y domain.

Surface

• Subagent

Sketch (optional)

File: agents/accessibility-auditor.md

Scope:

• WCAG 2.1 AA violation detection in HTML/JSX/TSX
• ARIA misuse: incorrect roles, missing required attributes, redundant roles
• Keyboard navigation issues: focus traps, missing skip links, focus order
• Screen-reader anti-patterns: non-descriptive link text, missing alt text, dynamic content without live regions
• Contrast ratio evaluation (flagging, not computing — suggest tooling)

Wired principle: swe-workbench:principle-accessibility

Acceptance (optional)

• agents/accessibility-auditor.md exists with valid frontmatter and tools list
• scripts/validate.py passes
• Agent is registered in plugin.json
• principle-accessibility wired via Skill invocation