Fix scroll reveal replay flicker

[fabianzimber]

Motivation

• Prevent reveal animations from replaying (causing a visible flicker) when IntersectionObserver/viewport updates jitter or when the rich layer is swapped in after scroll.
• Ensure once-only reveals behave consistently for both individual reveals and reveal groups.

Description

• Changed useInView calls to once: false and removed the optimistic visible default so visibility is driven by an explicit seen-state.
• Added hasBeenInViewRef and a hasBeenInView state that is seeded using getViewportIntersectionRatio() in a useLayoutEffect, and locked once set to avoid replay on jitter.
• Updated React.useEffect logic to only set the seen state once (for once === true) and changed shouldReveal to rely on the locked seen state for once mode.
• Applied the same fix to both Reveal and RevealGroup components in src/components/scroll/scroll-reveal.tsx.

Testing

• Ran lint with npm run lint, which completed successfully but produced a single warning no-before-interactive-script-outside-document in src/components/layout/marketing-layout.tsx.
• Ran the test suite with npm run test:ci, and all automated tests passed (75 tests passed).

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Codex Task

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Project	Deployment	Review	Updated (UTC)
eva-website	Ready	Preview, Comment	Jan 14, 2026 11:07pm

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