Fix boss idle reset and preload map floors

[agustin-littlehat]

Summary

• reset boss idle animation when returning to idle movement
• preload map floor component textures during map loading so E1M1 floor panes are cached before traversal
• add focused coverage for floor texture URL selection

Validation

• node test/runtime/renderBundlePreloadUrls.test.mjs
• pnpm test
• pnpm build