Module data/scene-loader/cache/cache-api

Cache surface helpers for the scene loader.

The SceneLoader owns three cache layers:

• L0: in-memory DecompressedChunkCache of decoded zarr chunks (skips the Blosc decompression on reuse).
• L1: in-memory metadata/raw-chunk cache inside MultiLevelCachingStore.
• L2: persistent OPFS cache inside the same store.

These pure functions implement the typed get/clear/list API that the SceneLoader exposes (getCacheStats, listCachedDatasets, clearL0Cache, clearL1Cache, clearL2Cache, clearAllCaches). Pulling them out of the SceneLoader class lets the cache surface be tested in isolation and gives a single home for cache-API additions (eviction tuning, hit-rate telemetry, etc.).

Each helper gracefully no-ops when the corresponding cache layer is null — matching the behavior the SceneLoader had inline, where caches are absent under ?noCache or when the global config disables them.