chore: Configure inactive GPUI frame throttling (#2749)

## Summary

- update GPUI to include configurable inactive-window frame throttling
- cap inactive story windows at 2 FPS using a 500 ms frame interval
- adapt gpui-fps to the latest profiler feature and frame event APIs

## Test Plan

- `cargo fmt --all -- --check`
- `cargo check -p gpui-component-story`
- `cargo test -p gpui-fps` (11 passed)