Phase 3: Build Glossary Web Viewer (GitHub Pages)

## Overview

Create a static, searchable web interface for browsing the Spectrum Design System Glossary, deployed to GitHub Pages.

**Related**: RFC Discussion #661 - Spectrum Design System Glossary

## Deliverables

### 1. Package Structure
- Create `docs/spectrum-glossary/` package
- Add `package.json`, `moon.yml`, build scripts
- Follow pattern from existing docs sites (`docs/s2-tokens-viewer`)

### 2. Core Features
- **Search & Filter**: Full-text search across all terms
- **Category Navigation**: Browse by registry type (sizes, states, variants, etc.)
- **Term Detail View**: Show all metadata
- Definition (superordinate, description, characteristics)
- Platform variations
- Sources and references
- Related terms with cross-links
- **Export**: JSON, CSV download options
- **Deep Linking**: Direct URLs to specific terms
- **Mobile Responsive**: WCAG 2.1 AA compliant

### 3. Build System
- `scripts/build-glossary.js` - Compile registry data into static HTML
- Generate static API files in `api/v1/` directory
- Integrate with existing build pipeline

### 4. GitHub Pages Deployment
- Configure repository for Pages
- Create `.github/workflows/deploy-glossary.yml`
- Auto-deploy on changes to registry
- Target URL: `https://adobe.github.io/spectrum-design-data/glossary/`

### 5. Integration
- Link from existing Spectrum documentation
- Embed help links in Component Options Editor
- Reference in naming guide documentation

## Dependencies

- ✅ Phase 1: Enhanced schema and content (Completed in feat/add-design-system-registry branch)
- ✅ Phase 2: Platform extensions (Completed in feat/add-design-system-registry branch)

## Acceptance Criteria

- [ ] Glossary accessible at GitHub Pages URL
- [ ] All 179 registry terms searchable and browsable
- [ ] Mobile-responsive design
- [ ] WCAG 2.1 AA accessibility compliance
- [ ] Auto-deployment working via GitHub Actions
- [ ] Export functionality (JSON, CSV) working
- [ ] Load time < 2 seconds
- [ ] Search results < 500ms

## Estimated Effort

2-3 weeks

## Related

- RFC: https://github.com/adobe/spectrum-design-data/discussions/661
- Implementation Status: `GLOSSARY_IMPLEMENTATION_STATUS.md`

Read GLOSSARY_IMPLEMENTATION_STATUS.md and inspect the existing docs/s2-tokens-viewer pattern first. Then trace the registry data into scripts/build-glossary.js, the api/v1/ output, and .github/workflows/deploy-glossary.yml. Done means the 179 terms are searchable, browsable, exportable, accessible, responsive, and deployed at the stated GitHub Pages URL.

Written by the indexing model from the issue text.