Fix e2e on 11.12

[YogendraShelke]

Summary

Fixes three defects in IntroScreen's slide-position handling, all rooted in how SwipeableContainer reconciled activeIndex (React state) with the FlashList's real scroll offset. The previous code used an isInitializing flag flipped by a double requestAnimationFrame, which guessed at timing instead of tracking what was actually requested.

Problems Fixed

Problem 1

Reopening a page showed slide 1 instead of the slide in the Active slide attribute, and fired a spurious On slide change back to slide 1

Root cause

activeIndex initialized to 0 while initialScrollIndex rendered the attribute's slide, so state and screen disagreed on mount. The effect only re-scrolled when slide !== activeIndex, so a matching-but-wrong state was never

Fix

Seed activeIndex from the attribute via a useState initializer, and force the positioning scroll once on the first pass where width is known (hasAppliedInitialScroll), independent of whether activeIndex already matches

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Problem 2

The initial slide was reached with an animation, briefly leaving slide content unreachable for TalkBack/VoiceOver

Root cause

goToSlide always animated. activeIndex applies immediately and drives accessibilityElementsHidden / importantForAccessibility, so the slide exposed to screen readers was off-screen until the animation landed

Fix

goToSlide(pageNum, animated = true); the initial jump passes animated: false

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Problem 3

Using Next / Previous / pagination could snap back to slide 1 and report an extra slide change

Root cause

onMomentumScrollEnd fires for programmatic scrolls too, reporting the offset the list is leaving rather than the one it's heading to. That stale offset overwrote activeIndex and re-fired onSlideChange. A drag flag alone can't disambiguate: it's only cleared inside onMomentumScrollEnd, so a drag that produces no momentum event leaves it stuck true, and the next programmatic scroll's stale event is misread as a user swipe

Fix

Track pendingScrollTarget — the slide goToSlide actually requested. onMomentumScrollEnd ignores any event whose index disagrees with that target, clearing it once reached. onScrollBeginDrag clears the target so a user taking over is always honoured, which also prevents the target latching when a scroll emits no momentum event