Render immutable bundled Studio projects correctly

[w1ne]

Summary

• request hosted /p/:slug meshes by project identity and optional immutable revision
• render only returned/root geometry by default so boolean cutters and predecessor solids stay hidden
• replace indefinite kernel warm-up with immediate error reporting and a 15-second bounded timeout
• include the approved asset-bundle design and implementation plan

Root cause

The hosted client reposted raw KCAD source without complementary STEP files and rendered every captured construction feature. That caused missing-import failures, giant sphere/cube artifacts, and an indefinite warm-up banner after initialization errors.

Validation

• 95 web test files passed (628 tests)
• focused final run: 37 tests passed
• TypeScript typecheck passes
• gallery build regression passes
• independent pre-merge review approved with no Critical or Important findings