Add a touch-gesture opt-out to attachControl

Problem

attachControl always registers its touchstart, touchmove, and touchend pinch/orbit path. AttachControlOptions can decline pointer-down handling or report an external drag/pick, but it cannot leave touch gestures to an application-owned gesture state machine. An application that needs identical gesture arbitration across renderers must currently register stopImmediatePropagation listeners before calling attachControl; listener order becomes part of correctness and re-attaching controls can accidentally restore the native Lite gesture path.

Minimal reproduction

import { attachControl, createArcRotateCamera, createSceneContext } from "@babylonjs/lite";

const scene = createSceneContext(engine);
const camera = createArcRotateCamera(-Math.PI / 2, 0.92, 12, { x: 0, y: 0, z: 0 });
const detach = attachControl(camera, canvas, scene, {
  shouldHandlePointerDown: (event) => event.pointerType !== "touch",
});

// Despite the predicate, attachControl's touch listeners still process a two-finger pinch.
// There is no option that reserves all touch gestures for the application's own handlers.
detach();

Proposed API

Add an opt-in field to AttachControlOptions, for example:

export interface AttachControlOptions {
  handleTouch?: boolean; // default true for backward compatibility
}

attachControl(camera, canvas, scene, { handleTouch: false });

When false, attachControl should not register or process its touchstart, touchmove, touchend, touchcancel, or gesture* listeners. Pointer events whose pointerType is "touch" should likewise not start camera rotation. Detach and re-attach should preserve the option with no duplicate listeners.

Alternatives considered

• shouldHandlePointerDown cannot disable the separate native touch-listener path.
• Reporting every touch as an external drag/pick couples camera controls to application state and still installs competing listeners.
• Capture-order stopImmediatePropagation blockers work, but are fragile across re-attachment and make listener ordering observable application behavior.

Current downstream workaround

Digipology installs four blockers before the first attachControl, retains them across camera detach/re-attach, and removes them on adapter disposal: blockLiteTouchGesture and mount ordering, listener registration before attachCamera.