Adds an arm64-simulator stub slice to llama.xcframework so consumers can build for the iOS Simulator.
All llama usage in OnDeviceCatalyst is guarded with #if !targetEnvironment(simulator), so the stub is only linked — never executed — on simulator builds.
Checksum: 741c3b584228c290c06bfbced9db161c3e7cb920c85d4d8df4ec54e8188a4e39