- Add `persistence.rs` for stable serialization of dock layouts without runtime identifiers.
- Introduce `preview.rs` for geometry handling of dock drop previews.
- Create `sizing.rs` to manage content-aware sizing policies and constraint solving for dock panels.
- Implement `welcome.rs` to provide a welcome surface when no documents are open, featuring New and Open actions.
- 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.
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