fix: recalculate spotlight overlay position on scroll events

[Arsh-sudo]

Summary

Closes #913

Fixes the spotlight overlay drifting away from its target element when
the user scrolls during the onboarding tour.

Root Cause

The spotlight used getBoundingClientRect() to position itself, which
returns viewport-relative coordinates. When the user scrolled, the stored
targetRect became stale — the coordinates no longer matched the element's
actual position — causing the spotlight to highlight unrelated content.

The component already had a resize listener that re-measured on window
resize, but no equivalent for scroll events.

Fix

Added a scroll event listener alongside the existing resize listener in
the re-measure useEffect:

window.addEventListener("scroll", remeasure, true);

Using capture phase (true) ensures scroll events from nested scrollable
containers are also caught, not just window-level scrolling.

The cleanup function removes both listeners correctly on unmount.

Files Changed

• src/components/OnboardingTour.tsx — added scroll listener, renamed
  onResize to remeasure for clarity

Testing

1. Start the onboarding tour
2. Scroll the page during any step
3. Spotlight should remain anchored to the target element

[vercel]

@Arsh-sudo is attempting to deploy a commit to the magic-peach1's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

👋 Thanks for your PR, @Arsh-sudo!

Welcome to Reframe — a browser-based video editor built for everyone 🎬

What happens next

1. 🤖 Automated checks — build & TypeScript typecheck will run automatically
2. ✅ Vercel preview — a preview deployment will be created (requires maintainer authorization for fork PRs)
3. 👀 Code review — a maintainer will review your changes
4. 🚀 Merge — once approved, your PR will be merged!

Quick checklist

• PR title follows Conventional Commits (e.g. feat: add dark mode)
• Linked the issue this PR closes (e.g. Closes #123)
• Tested the changes locally (bun run dev)
• Build passes (bun run build)

Useful links

• 📖 CONTRIBUTING.md
• 🐛 Open Issues
• ⭐ Star the repo to support the project!

Happy coding! 🎉

[github-actions]

✅ PR Format Check Passed — @Arsh-sudo

Basic format checks passed. A maintainer will review your code changes.

This does not mean the PR is approved — it just means the format is correct.

[Arsh-sudo]

Performance Improvement

Wrapped the remeasure callback in requestAnimationFrame to prevent
layout thrashing on rapid scroll/resize events. Any pending frame is
cancelled before scheduling a new one, binding recalculation strictly
to the browser's rendering cycle.

[magic-peach]

Merged! This cleanly fixes the spotlight overlay drifting during scroll — adding a scroll listener with capture phase alongside the existing resize listener is exactly the right fix. Using requestAnimationFrame to debounce rapid events is a nice touch too. All CI checks passed. Great work @Arsh-sudo!