Add STL mesh parsing and gallery imports

[agustin-littlehat]

Summary

• add ASCII/binary STL parsing, metadata, loadMesh dispatch, and conservative STL optimization behavior
• add STL import/gallery support with curated CAD presets and docs updates
• allow vertical orbit rollover across vanilla, React, and Vue controls
• extend compat-hunter and corpus bench tooling for STL hunts

Verification

• pnpm --filter './packages/' -r --if-present test\n- pnpm --filter './packages/' -r build\n- pnpm --filter @layoutit/polycss-website build\n\n## Notes\n- Polyminer files are intentionally excluded from this PR.