feat(pdftract-2825c): implement inspector frontend bundle with <80KB size limit
Phase 7.9.3: Frontend bundle (HTML + CSS + JS) via include_bytes!
- Created vanilla web app frontend (no framework, no CDN)
- index.html (1,963 bytes raw)
- style.css (3,291 bytes raw) with CSS-only layer toggles
- app.js (5,494 bytes raw) with localStorage and keyboard shortcuts
- Bundle size: 10,748 bytes raw, 3,914 bytes gzipped (well under 80KB limit)
- Features:
- 8 layer toggles via CSS data attributes
- localStorage persistence (namespaced "pdftract-inspector-*")
- Keyboard shortcuts: ArrowLeft/Right, '/', 1-8 for layers
- URL fragment navigation (#page=N)
- Search with debouncing
- Offline-capable (no external dependencies)
- Updated inspect.rs to serve frontend via include_str!
- Added build.rs bundle size check with libflate
- Added libflate as build dependency
Refs: pdftract-2825c
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>