feat: add audio-only export option (MP3/AAC)

[choudharyms]

Description

This PR adds functionality to extract the audio track directly from an uploaded video using the ffmpeg WASM engine.

• Extended EditRecipe and ExportResult types to support mp3 and aac, adding them to the UI Format Selector.
• Refactored VideoEditor to dynamically hide video-specific UI panels (Rotate, Adjustments, Framing, Output Size) when an audio format is chosen for a cleaner UX.
• Configured the export engine to skip the video stream (-vn) and mapped appropriate audio codecs (libmp3lame and aac).
• Patched a legacy CDN loading bug in ffmpeg.ts where the WebAssembly SIMD check attempted to fetch a deprecated @ffmpeg/core-simd binary instead of the standard core.

Related Issue

Closes #134

Type of Contribution

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

Participant Info

• GitHub username: @choudharyms
• Contribution level (Beginner/Intermediate/Advanced): Intermediate

Checklist

• I have read the contribution guidelines
• My changes follow the project structure
• I have tested my changes
• This PR is related to a valid issue

Reframe.Resize.trim.and.export.videos.in.your.browser.-.Google.Chrome.2026-05-19.11-24-24.mp4

[vercel]

@choudharyms 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, @choudharyms!

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 Check Passed — @choudharyms

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.

[choudharyms]

Hi @magic-peach ,

Thank you for the feedback!

Feature Branch: I have closed the previous PR and created a new clean feature branch (feat/audio-export) as requested. I've re-opened the new PR from this branch.
Merge Conflicts: All conflicts have been resolved against the latest main branch.
FFmpeg CDN & SIMD Loading: I verified the loading logic. The implementation keeps the upstream loader (loadFFmpeg) completely untouched—meaning it uses the standard multi-threaded/single-threaded cores loaded via unpkg.com and remains 100% compatible with the project's current loader structure.
All local TypeScript checks (tsc --noEmit), lints, and the Vitest test suites are passing cleanly (77/77 tests passed).

Looking forward to your review!