bug: FPSCounter does not display real FPS count

Currently, FPSCounter runs its own requestAnimationFrame loop. As a result, it effectively displays the screen's refresh rate.

I created a simple example that demonstrates the issue:

https://github.com/user-attachments/assets/adda6f64-7d72-4ba2-a543-11654abed80e

In this example:

• I dispatch a heavy compute pipeline
• I then dispatch a render pipeline that depends on the compute pipeline's resources, making dropped frames visible
• The example's RAF loop explicitly waits for the device to finish its work

We can observe that:

• The example's RAF timing closely matches the GPU frame time
• Our FPSCounter starts dropping because the GPU is under heavy load and the browser no longer can deliver frames at the full speed

I looked at how Three.js implements their fps counter. Their approach is not practical for us because they inject the inspector directly into the renderer (which we don't have).

Start by locating the FPSCounter implementation and reproduce the linked example with its heavy compute and dependent render pipelines. Trace how the counter's requestAnimationFrame loop measures frames, then verify that the reported value reflects completed GPU work rather than only display refresh timing.