Prefetch nearby scene assets in the background

crates/libremetaverse/CHANGES.md

@@ -37,3 +37,11 @@ Files: `src/grid_manager.rs`, `src/client_core.rs`.
   the existing UDP asset transfer path instead of reporting a missing asset immediately.
 
 File: `src/asset_manager.rs`.
+
+## Deterministic persistent-asset LRU
+
+- Successful immutable asset-cache reads explicitly refresh the file modification timestamp.
+  Pruning uses that timestamp as its cross-platform LRU order instead of filesystem access time,
+  which can be disabled or coarsened by `noatime` and `relatime` mounts.
+
+Files: `src/asset_cache.rs`, `src/asset_pipeline_semantics.rs`.