Migrate NumericInput slider to pointer events

[willeastcott]

Summary

• Replace mouse events (mousedown, mouseup, mousemove) with pointer events (pointerdown, pointerup, pointermove) for consistency with the Container component's resize handle
• Add pointer ID tracking to prevent multi-touch interference
• Works correctly even when pointer lock is unavailable or denied

Details

The NumericInput slider control now uses pointer events instead of mouse events, aligning with the pattern established in the Container component. Pointer ID tracking ensures only the pointer that initiated the drag can control or end it, making the component robust for multi-touch scenarios and browsers where pointer lock may not be supported.

The existing Pointer Lock API usage is preserved for infinite scrubbing functionality. Event constant names (EVENT_SLIDER_MOUSEDOWN, EVENT_SLIDER_MOUSEUP) are kept for backward compatibility.

Test plan

• Verify slider drag works with mouse
• Verify slider drag works with touch (if available)
• Verify pointer lock still provides infinite scrubbing
• Test in browser without pointer lock support (slider should still work)