Group the bgm spec cluster under docs/bgm and move dev logs and plans under docs/status, add an overview index, and update cross-references in the docs, README, and source comments.
Model ColorDiffuse in shared types and multiply each viewer's material color by the per-object tint, including textured faces and loaded custom models.
Add a /mod/:id/setup page that lays out every renderable object in a single shared scene. Export object-facing mesh wrappers from the viewers and share geometry and materials across objects via module-level caches.