Whole-file loading still failed after adding caching because the public proxy interrupted large GLB response bodies. Download validated 1 MiB ranges, retry transient failures up to three attempts, and persist completed chunks so reloads resume from their last boundary.
Add regression cases observed failing before the change for interrupted downloads, cross-reload resume, and temporary HTTP failures. Verify range integrity, full-cache reuse, permanent errors, and storage fallback.
Persist versioned models and validated network metadata in IndexedDB. Show scene download progress and recoverable errors with the existing frosted material.
Connect existing skeletons to pending navigation and route boundaries while preserving the map. Previously only dynamic imports showed fallbacks, and rejected model promises prevented retries.
Verified: 32 focused unit tests; 4 navigation and scene browser checks; 7 cache browser checks including invalid-metadata recovery; isolated production build and type checks.
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