fix(android): cancel the JS touch when the pager starts dragging

[Luccacvb]

Summary

Fixes the Android case of #424, which reports this on Android and on iOS. Related: #960, #954.

In 9.x, on Android, a swipe that starts on a Pressable inside a page never sends touchcancel to JS. Every such swipe ends with touchend, so the Pressable can fire onPress when the dragging event reaches JS late, for example while the JS thread is busy. This is #960 coming back in 9.x.

reproduction

pager-view-before-after.mp4

What happened

• 8.x called NativeGestureUtil.notifyNativeGestureStarted from NestedScrollableHost.onInterceptTouchEvent once the touch passed the slop (fix(android): prevent taps while scrolling #961), so React Native cancelled the JS touch, as it does for ScrollView.
• 9.0.0 (feat(android): jetpack compose support #1092) removed NestedScrollableHost.kt, and the call was not ported to ComposePagerView. Only the JS guard is left, and it depends on when the dragging event arrives.

Fix

• ComposePagerView notifies React Native from onInterceptTouchEvent when the touch moves touchSlop along the pager axis, where the Compose pager starts dragging, and ends the native gesture on ACTION_UP, like ReactScrollView.
• Mouse drags are skipped, since the Compose pager does not drag with a mouse. Nothing changes when scrollEnabled is false.
• Once the pager starts dragging from a touch on page content, JS gets touchcancel instead of touchend, as in 8.x.
• This touches the same dispatchTouchEvent block as fix(android): let nested horizontal ScrollView scroll inside pager #1182, so whichever lands second needs a small rebase. I can do it here.

Test Plan

What's required for testing (prerequisites)?

Android emulator or device.

What are the steps to reproduce (after prerequisites)?

Added Issue #424 Swipe Cancels Press Repro to the example app and e2e/tests/issues/issue-424-swipe-cancels-press.e2e.ts:

1. Tap the button on page 0: it is pressed (control).
2. Swipe to page 1 starting on the button. Before: Touch: end. After: Touch: cancel.
3. Tap Block JS, then do the same swipe. Before: Presses: 1, the swipe pressed the button. After: Presses: 0, Touch: cancel.

Verified

• format:check, lint (no new warnings), typecheck, prepare, test, example typescript and e2e typecheck pass.
• On main, 2 of the 3 new tests fail (the tap control passes). With the fix all 3 pass. Same result on every run. Android 16 emulator (arm64), release build.
• Full Android e2e suite with the fix: 17/17 tests pass.
• By hand on a Redmi Note 5 (Android 9) with the fix: a tap presses the button, a swipe from it gives Touch: cancel, and a swipe from it while JS is blocked leaves Presses: 0.
• Scratch screen with a PanResponder in a page: a horizontal drag on it gives the same callbacks on main and with the fix (grant, then terminate, and the page changes).

iOS is untouched.

Compatibility

OS	Implemented
iOS	n/a
Android	✅

Checklist

• I have tested this on a device and a simulator
• I added the documentation in README.md: not applicable
• I updated the typed files (TS and Flow): not applicable

[Luccacvb]

Resolved the conflicts with #1182. The only change is that the slop check now uses rawX/rawY, following #1182