Add workflow infrastructure — ESLint, Prettier, Husky, Vitest, 7 new skills

Phase 1: Session log archived (1096→91 lines), D031 token access convention
Phase 2: ESLint v9 + Prettier + jsx-a11y, initial config and lint fixes
Phase 3: 7 new skills (polish, harden, normalize, clarify, typeset, quieter, adapt)
         + Vercel reference docs, updated audit/review-component refs
Phase 4: Husky + lint-staged pre-commit hooks, preflight updated to 8 checks
Phase 5: Vitest + Testing Library + /write-tests skill

- Badge.tsx colour maps unified to CSS variables (D031)
- 5 empty interface→type alias fixes (Switch, Radio, Divider, IconButton, Link)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/reference/vercel/web-design-guidelines.md

@@ -0,0 +1,39 @@
+---
+name: web-design-guidelines
+description: Review UI code for Web Interface Guidelines compliance. Use when asked to "review my UI", "check accessibility", "audit design", "review UX", or "check my site against best practices".
+metadata:
+  author: vercel
+  version: "1.0.0"
+  argument-hint: <file-or-pattern>
+---
+
+# Web Interface Guidelines
+
+Review files for compliance with Web Interface Guidelines.
+
+## How It Works
+
+1. Fetch the latest guidelines from the source URL below
+2. Read the specified files (or prompt user for files/pattern)
+3. Check against all rules in the fetched guidelines
+4. Output findings in the terse `file:line` format
+
+## Guidelines Source
+
+Fetch fresh guidelines before each review:
+
+```
+https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md
+```
+
+Use WebFetch to retrieve the latest rules. The fetched content contains all the rules and output format instructions.
+
+## Usage
+
+When a user provides a file or pattern argument:
+1. Fetch guidelines from the source URL above
+2. Read the specified files
+3. Apply all rules from the fetched guidelines
+4. Output findings using the format specified in the guidelines
+
+If no files specified, ask the user which files to review.