fix(web): use Pointer Events API for touch support in HtmlElementContainer

[omnisonic]

Issues

Fixes #2634

Proposed changes

Replace mousedown/mousemove/mouseup DOM event listeners with the Pointer Events API (pointerdown/pointermove/pointerup) in HtmlElementContainer.ts.

PointerEvent extends MouseEvent, so BrowserMouseEventArgs remains fully compatible — pageX, pageY, button, and preventDefault() all work identically. The change is backward compatible for existing mouse-based users.

Files changed:

• packages/alphatab/src/platform/javascript/HtmlElementContainer.ts — swap event names
• packages/alphatab/src/platform/javascript/BrowserMouseEventArgs.ts — update type annotation from MouseEvent → PointerEvent

Tested on:

• Desktop mouse (existing behavior unchanged)
• iPhone Safari — beatMouseDown, beatMouseMove, beatMouseUp all confirmed firing on touch
• Lenovo Android tablet, Firefox 149 — all three events confirmed firing on touch

Checklist

• I consent that this change becomes part of alphaTab under it's current or any future open source license
• Changes are implemented
• New tests were added — no browser event testing infrastructure exists in the current test suite; this is a DOM event wiring change that requires a real browser environment to test. All 1448 existing tests pass.

Further details

• This is a breaking change
• This change will require update of the documentation/website