OfflineToggleable

Mixin for cache-aware sources / factories that can flip between online and offline modes at runtime. Lets app-level "go offline" walks dispatch generically across CachedTileSource (image / vector / feature pyramids) and the elevation factories (CachedElevationSourceFactory, GpkgCachedElevationSourceFactory).

When isCacheOnly is true, fetch paths never call the upstream network source; cache misses return null (or the layer's equivalent of "no data"). Implementations should respond to runtime toggles without re-wiring.

Inheritors