- ignore assets/models/blender_src/*.blend (keep the .gdignore marker tracked) and
remove the 46 editable .blend files from the index; they remain on disk and are
regenerated by tools/blender_assets.py
- move the completed storage/docs/code-path/art-loader/verification, mouse-fix,
and pop-up sections to DONE.md; TODO now holds only the open lighting item,
realism follow-ups, and optional ideas
- docs changes only; runtime code unchanged