feat : added a video preview feature

[AarishMansur]

Description

Implements #1052 — adds a Preview Frame button that extracts a single
frame at the midpoint of the trimmed range using FFmpeg.wasm, applying the
full filter chain (crop, rotation, speed, color) so users can verify
settings before a full export.

Files changed:

• src/lib/ffmpeg.ts — added generatePreviewFrame()
• src/hooks/useVideoEditor.ts — added preview state + action
• src/components/PreviewPanel.tsx — new preview component
• src/components/VideoEditor.tsx — integrated PreviewPanel into sidebar

Also fixes FFmpeg loading to use fetchWithIntegrity() with jsdelivr URLs
introduced in this PR was still pointing to unpkg.com causing
exports to fail locally.

Related Issue

Closes #1052

Type of Contribution

• New feature
• Bug fix
• Documentation update
• Refactor
• GSSoC contribution

Participant Info

• GitHub username: aarishmansur
• Contribution level: Advanced

Screen Recording

cursorful-video-1779624562208.mp4

Checklist

• I have read the contribution guidelines
• My changes follow the project structure
• I have tested my changes in Chrome, Firefox, and Safari
• bun run lint passes
• bunx tsc --noEmit passes
• New interactive elements have aria-label / accessible names
• No console.log statements left in
• This PR is related to a valid issue
• Screen recording attached above

[vercel]

@AarishMansur 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, @AarishMansur!

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

🟠 GSSoC'26 PR detected — thanks for contributing under GirlScript Summer of Code 2026!

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 Issues — @AarishMansur

Please fix the following before your PR can be reviewed:

• ⚠️ Use a conventional PR title. Examples:
  • feat: add dark mode support
  • fix: resolve aria label missing on slider
  • docs: add deployment guide to README

Push new commits after fixing — this comment will update automatically.

📖 CONTRIBUTING.md