BundledSourceHandler class

Handles installation of models from native bundled resources

Features:

• Uses platform-specific native resource paths
• Android: assets/models/{resourceName}
• iOS: Bundle.main.path(forResource:)
• Web: /assets/{resourceName}
• No copying required (uses native path directly)
• Single-step progress (resources already available)

NOTE on targetFilename: a bundled resource is compiled into the app at a fixed BundledSource.resourceName — this handler cannot rename the physical asset at runtime. targetFilename only namespaces the repository identity key (ModelInfo.id); it does not affect getBundledResourcePath. Bundled companions are not among today's exposed collisions (network installs are); this closes the repository-key ambiguity for future bundled companions without claiming to fix an on-disk collision this handler structurally cannot fix.