feat: pipedal SVG icons in block tiles + nav bar
- Replace emoji getBlockIcon() with <BlockIcon> component rendering SVG icons
- 38 fx_*.svg icons from pipedal mapped to block types (distortion, delay, reverb, mod, etc.)
- Split/merge tiles now use fx_split_a.svg / fx_mixer.svg
- Status bar: ic_bank.svg, ic_presets.svg, fx_analyzer.svg, ic_drawer_2.svg
- Extracted reusable CSS design system to index.css (badge, snap-grid, slide-panel, etc.)
- SnapshotPanel and component reference extracted to docs/
- 270KB JS build, SVG icons served from /ui/img/
shawn
62c373b989