92676a5875f4b585fb7bc98aa5016b79947f2176  iPad Trackpad: Remote subframes can get stuck with a stale hovering pointer when switching to touch

Classified as not security-relevant.
Triage note: Adds EventHandler::mousePointerDidDisappear()/clearLastKnownMousePosition() wired from continueWheelEventHandling for non-UserDriven momentum phases, and a null guard in fakeMouseMoveEventTimerFired (previously valueOrDefault, already safe). Behavioral/UX change for hover state, not a memory-safety or logic-security fix.
This commit was flagged by the signal scorer and reviewed by AI (not a human). It is listed only so the triage is auditable; there is no root-cause analysis because this is not a vulnerability fix.

Structural signals: smartptr_member_added (+4.87), null_guard (+1.2)