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.
Keep the control panel geometry stable when toggling building context, and use accessible switch controls to prevent focus-driven movement. Add browser coverage for camera framing, opacity, responsive layout, and the default 6x pipe scale.
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