- remove dead 3D code: App/GemhallScene/SplashScene/ModelScene (unreferenced
since the 2D pivot) + the three dep and its empty manualChunk
- drop public/models (68MB of unused KayKit/poly-pizza GLBs)
- dist drops ~36MB -> 2.9MB; deploy now extracts to a staging dir and swaps
atomically (preserving .well-known), so users never see a mixed/stale state
and stale chunks no longer accumulate (28 -> 7 assets on the server)
- booth: welcoming first-run onboarding (3 steps to go live) replacing the
bare 'no classes yet' hint
- verified live: 2D home renders, 0 failed requests, booth welcome shows