fix: improve DOM processing for the toolbar (#42208)

with recent changes the toolbar went from freezing my browser with the clickmap to taking 20 seconds to process events against the DOM

![Screenshot 2025-11-27 at 14.06.59.png](https://app.graphite.com/user-attachments/assets/4675ca0a-c073-4603-8e5b-2c84c0f2dc06.png)

there is multiple repeated calls to matchEventToElement which traverses the DOM to find a selector

let's introduce a bunch of optimisations since a lot of look-ups could be O(1) against a map

we also show progress as we go, so the user knows what is a-happening

![Screenshot 2025-11-27 at 14.30.58.png](https://app.graphite.com/user-attachments/assets/a5eea207-5deb-4d21-99b6-2e85b48a25da.png)

Author: pauldambra