refactor(virtual-core): extract the iOS touch gesture into IosGesture (#1325)

Moves the iOS touch gesture state out of the Virtualizer into an internal IosGesture class. The late-fling window is now a gesture phase. A waiting command keeps its fling samples. One fix: a scroll-element change no longer carries over a pending late-fling window.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: piecyk

.changeset/ios-gesture.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/virtual-core': patch
+---
+
+refactor(virtual-core): move the iOS touch gesture tracking into its own internal module. One fix along the way: changing the scroll element no longer carries over a pending iOS late-fling window, which could defer corrections on the new element for 150ms.