Runtime Tile Texture Ownership

RuntimeTileCache is the authoritative owner of decoded runtime tile payloads. Mapv10ThreeRenderer may create THREE.DataTexture objects from those payloads, but those textures must be disposed synchronously when the runtime tile is evicted.

The renderer subscribes to RuntimeTileCache.onEvicted(...) and tears down all per-tile terrain texture caches keyed by the evicted runtime tile. This keeps GPU texture residency, JavaScript typed-array reachability, and cache byte accounting in the same lifecycle. Terrain scene-node disposal still performs the same per-key cleanup as a secondary path for normal mesh fade-out.

For the broader cache architecture, eviction scoring, and family-floor budgets, see ../../../docs/viewer.md § Cache Architecture.