Initial release.

• Unified, multi-provider game-services facade: achievements, leaderboards, stats, cloud save, profiles, rich presence and friends behind one API.
• Write operations fan out to every capable provider; reads come from the primary provider (or one chosen with from:), with per-provider failures aggregated into AggregateGameServiceException.
• Capability gating (supports / supportsEverywhere), merged event stream, and typed access to provider-specific APIs via provider<T>().
• dispose() fans out to every provider to release timers, HTTP clients and native SDK handles.