Reduce duplicate 3D model loading for cachebusted URLs

[itsdior01]

Summary

• Reuse the same loaded 3D model when only cachebust_origin changes in the model URL.
• Add a unit test covering repeated model URLs.
• Keep other URL parameters in the model identity so different models still load separately.

Fixes #93

Checks

• Passed: bun test tests/global-obj-loader.test.ts
• Passed: changed files format check
• Passed: npm run build
• Passed: npm run test:node-bundle

Note: the full bun test suite still has unrelated board/SVG failures that were not touched by this change.

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Project	Deployment	Actions	Updated (UTC)
3d-viewer	Ready	Preview, Comment	May 20, 2026 1:22am