- Add `selection/state.rs` to manage selection masks, including combining masks and calculating bounds.
- Introduce `vector_edit.rs` for vector shape manipulation, handling drag sessions, and hit testing for handles.
- Create `feature_scorecard.rs` to ensure stable feature identifiers and regression gates for GUI components.
- Implement raster behavior tests in `raster_test.rs` to validate gradient application against masks.
- Added marching_ants_offset to HcieIcedApp for animation state
- Added selection_bounds field to IcedDocument for persistent selection display
- Updated OverlayProgram to draw animated marching ants (black + white dashed lines)
- Added timer subscription for continuous animation when selection is active
- Updated SelectAll/Deselect handlers to properly manage selection state
- Selection now remains visible after creation with animated border
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