Ultrono Arena macOS client

Build ref: 1e5584554ddf
Branch: master
Built at: 20260828T132042Z
Architectures: x86_64 arm64
Deployment target: macOS 11.0

This is the Lean-backed Rust client. The executable has no package-manager
dynamic-library dependencies. Sounds are the deterministic public CC0 pack.

Double-click Ultrono Arena.app to start the client.
User-editable config is stored in ~/Library/Application Support/Ultrono Arena.
