Clone cached OBJ models safely

[phungkaizen]

Summary

• Add cloneLoadedObject so cached OBJ loads return independent object trees while reusing geometry.
• Clone mesh materials for each cached instance to avoid shared mutable material state between viewers.
• Use the clone helper for cache hits, pending cache promises, and first-load cache storage returns.
• Add a regression test for cached model cloning behavior.

Fixes #93
/claim #93

Review & Testing Checklist for Human

• Verify repeated use of the same model URL no longer shares mutable object/material state between rendered instances.
• Confirm cached geometry reuse does not regress model display or memory behavior.
• Check preview/Storybook with repeated OBJ footprints if available.

Notes

Tested locally:

• bun test tests/global-obj-loader-cache.test.ts
• bun run build
• bunx --bun tsc --noEmit

Full bun test currently has pre-existing failures unrelated to this change in existing outline/preprocess suites.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
3d-viewer	Ready	Preview, Comment	May 12, 2026 7:44pm

[phungkaizen]

Hi maintainers, I added validation details for this focused OBJ cached clone fix.

Validation:

• GitHub checks are passing, including test, type-check, and format-check.
• Vercel preview is Ready.
• The PR includes regression coverage for cached OBJ clone behavior.

Minimal demo/GIF plan:

1. Open a preview scene with repeated OBJ models using the same source URL.
2. Confirm the model is loaded through the cache path.
3. Confirm each rendered instance has an independent cloned Object3D tree.
4. Confirm geometry is reused while materials are cloned per instance, so hover/transparency state does not leak between repeated models.

I’m happy to add an actual short GIF/video if needed for review.