[spdermn02]

Summary

While the 3D editor loads, the view cube's placeholder and the box in the middle of the view are
each drawn as three clip-path faces, and they did not look like cubes:

• The top face's lower edges and the side faces' upper edges ran at different slopes, so the gaps
  between the faces were wedges (about 28 px at the outer corners, 12 px in the middle), and on
  the small cube the top overlapped the sides.
• The shimmer's border-radius rounded two corners of each side face and none of the top's.
• The placeholder stood 28 px from the edge while the real view cube stands at 10 px, so it jumped
  sideways when the editor appeared.

Both are now 2:1 isometric cubes with even seams (6 px on the box, 3 px on the small cube) and
sharp corners, and the placeholder stands where the real cube will (left or right, 10 px).
CSS only: globals.css, viewCube.css, plus a changelog entry.

Testing

• npm run typecheck
• npm test (plus npm run test:e2e, npm run build, npm run export; no committed file
  changed by the build; npm run theme:graphite leaves the theme unchanged)
• Manually tested the affected workflow (the loading screen, before and after side by side)

Notes

• No storage, import, export, grouping or undo/redo changes.
• On a narrow or flat window the real cube shrinks to about 80%; the placeholder still does not,
  as before.

🤖 Generated with Claude Code