Feature: Enable 120Hz rendering on ProMotion displays

Currently, MTKView defaults to rendering at 60 FPS. On ProMotion displays (iPhone 13 Pro and later, iPad Pro), we could enable 120 Hz rendering for smoother splat visualization.

Proposed Change

Set preferredFramesPerSecond to screen.maximumFramesPerSecond during MTKView initialization.

Would this be welcome as a pull request? I’d be happy to contribute this improvement.