- Added specifications for Phase 10a, introducing permanent size changes to `.prop` documents and reversible uniform instance scaling in Sandbox EDIT mode.
- Updated `PropCanvas`, `PropAnchorData`, `PropEditor`, `StageGizmos`, `SandboxStage`, and `StageSelection` classes to support new scaling features.
- Implemented document transactions for scaling, including normalization to a 96 px maximum dimension.
- Introduced a new **Transform Whole Prop** tool in the Prop Editor for moving, rotating, and resizing props.
- Created unit tests for the new scaling functionality, validating shape scaling, anchor transformations, and whole-prop interactions.
- Ensured compatibility with existing prop formats and maintained the integrity of the document structure during scaling operations.
- Implemented test_phase9a_prop_attach.gd to validate anchor schema, alignment math, and preview isolation.
- Implemented test_phase9b_prop_centering.gd to check canonical origin presentation, bounds, centering, and save threshold.
- Implemented test_phase9c_prop_editor_ux.gd to assess the user experience in the prop editor, including anchor renaming and UI responsiveness.
- Added corresponding .uid files for each test.
- Created sync_sources.py script to manage markdown file synchronization with the notebook.
- Added .gitignore for virtual environment files.
ryan