2.1.0

Added

• x86_64 in the iOS simulator slice. The slice is now ios-arm64_x86_64-simulator, like LibDovi's. A generic iOS Simulator build of a consumer links both architectures, and without x86_64 an app embedding AetherEngine failed to link with undefined truehd_atmos_* symbols. The tvOS and visionOS simulators stay arm64 only.

Same decoder, source and pins as 2.0.0; every other slice is a rebuild. harness/verify.sh passes in full (PCM bit-exact against truehdd, every slice links, x86_64 simulator included) and cargo test --release is 8/8.