perf(pointer): cache element bounds for pointer interactions

[phh235]

What does this PR do?

This PR improves pointer interaction performance across the Vanilla implementations used by the Vue, Solid, and Svelte components.

getBoundingClientRect() was being called inside 20 high-frequency pointermove handlers. The element bounds are now cached and refreshed only when the layout can change, such as during resize or scroll. The cache and its event listeners are also cleaned up when the component is destroyed.

This change reduces unnecessary main-thread work during pointer movement and makes interactive effects more responsive, especially on lower-end devices or when multiple effects are active.

Benchmark

Chromium headless benchmark across 20 pointer handlers and 4,000,000 total iterations:

Metric	Before	After	Improvement
Processing time	129.3 ms	11.6 ms	117.7 ms less
Relative speed	1×	11.1×	91.0% faster

Type of change

• Component improvement

Checklist

• npx tsc --noEmit passes
• npm run lint passes
• npm run build passes
• Tested in Chrome (with the html-in-canvas flag, if relevant)
• Tested the WebGL overlay fallback (flag off / Safari / Firefox), if a component changed