viewer/bridge_scene.rs: BridgeScene compositor - 5× PSC-I Girder (2500mm c/c) - DeckSlab (12000mm, 220mm thick, top of girders) - 10× Elastomeric Bearing (5 per abutment end) - 2× ReverseT Abutment (start & end) - sweep::merge_meshes로 단일 메시 합성 - scene_extents()로 카메라 자동 배치 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>