Showcase: Progressive LOD Loading & Context-Loss Poster Fallback for VECTOR 3D on Mobile

Sharing our engineering notes from deploying high-poly industrial assets across web showrooms: 1. Keep heavy 3D bundles out of the initial static import graph until viewport readiness; 2. Cap device pixel ratio on mobile with adaptive resolution scaling, and swap seamlessly to a camera-matched prerendered poster on `webglcontextlost` with one-click retry.