- Add mask selector with previews to the brush card (data-driven from
painter.brushMasks); persist activeBrushIndex with HUD layout.
- Fix alpha/coverage artifacts when overpainting after load or backend
switch: derive the dilation source marker from a deterministic UV island
mask instead of resetting it to "unpainted" on every seed.
- Import the two final brush mask textures (Brushes/).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
