Add 18 artisan examples and tag-based gallery filtering

18 new examples showcasing underrepresented features:
- Woodcut Landscape: heavy hatching, distortion, brush strokes
- Art Deco Sunburst: path decorators, bilateral symmetry, gradients
- Sumi-e Bamboo: brush strokes, warp transform, stipple
- Memphis Pattern: pattern fills, scatter
- Celtic Interlace: grid symmetry, path decorators
- Halftone Layers: halftone filter, compositing blend modes
- Paper Collage: grain filter, distortion, hatching, stipple, shadows
- Botanical L-system: L-systems, stippled flowers, hatched leaves
- Type Poster: text-clip, gradient fills, drop shadow
- Contour Terrain: contour lines, hatched water, decorated compass
- Watercolor Blooms: multiply compositing, translucent pastels
- Geometric Tiling: grid symmetry, star patterns, hatching
- Pointillist Landscape: scatter, noise variation, gradient mapping
- Woven Ribbons: group clipping, animated sine weave
- Vintage Map: contours, hatching, stipple, decorators, text
- Glitch Art: posterize and duotone filters, screen compositing
- Spiral Text: text-on-path, Archimedean spiral
- Morphing Geometry: shape morphing through polygon cycle

Gallery now has tag-based filtering:
- Each example has :tags metadata (feature keywords)
- Filter bar at top of gallery page with clickable tag pills
- Clicking a tag shows only matching examples, hides empty sections
- Tag pills shown on each gallery card
- Total: 100 examples across 8 categories

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

Author: leifericf