M5.5: effect masks (ellipse / 4-point polygon / pen Bezier) with keyframable path, feather, opacity, expansion, inverted, modes; opacity masks; WGSL coverage parity; on-monitor editing
- project:😷 MaskPath (cubic Bezier, clip pixels) as ParamValue::Path (vertex-wise keyframe interpolation), Mask, MaskMode, TrackMethod; schema v7 (no-op migration)
- render:😷 analytic antialiased coverage via signed distance + feather falloff in linear light; masked effect = lerp(original, effected, coverage); opacity masks before Motion; adjustment layers
- gpu::GpuMask: same coverage + mix in WGSL compute (max |cpu-gpu| ~3e-6)
- engine masks.* commands (add/remove/set/moveVertex/translate/addVertex/removeVertex/toggleVertexSmooth/select/list); keyframe commands take "mask"
- UI: Effect Controls mask rows; Program monitor overlay (vertices, handles, feather/expansion handles, body drag, pen tool) with automation ids
- goldens: mask_blur, mask_color, mask_inverted, mask_opacity
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>