- Add Menu scene with Rive-driven login and navigation UI
(RiveLoginController, RiveNavigationController) for entering a
username and starting/navigating the client via Rive triggers
- Add SceneTransitionController to fade out and load the Landscape
gameplay scene when Play is selected
- Add procedural low-poly triangle field background and animated wave
panel (LowPolyTriangleField, TriangleWavePanel) with matching
editor menus and materials
- Add MenuLightAnimator for animated menu lighting and UI fade helpers
(MenuFadeIn, DebugFadeToggle/Bridge)
- Rename SampleScene to Landscape and wire ChatNetworkManager to hide
the new Rive login canvas once gameplay starts
- Bump Input System action codegen version and add Rive package
references/project settings updates to support the new UI