feat: export history — show a session list of recent exports with re-download links

[magic-peach]

Once a user exports a video and starts working on another setting or file, the previous export result is gone. An export history panel would let users re-download past exports within the same browser session.

What to build

Maintain an in-memory list of ExportResult objects for the current session (max 5 entries). Display the history in a collapsible panel below the export button:

• Each entry shows: filename, format, file size, output dimensions, export timestamp
• A "Download" button re-triggers download from the stored blob URL
• A "Clear" button removes all history entries and revokes blob URLs

Note: blob URLs are only valid for the current session — make this clear in the UI ("History is cleared when you close or refresh the page").

Files to modify

• src/hooks/useVideoEditor.ts — add exportHistory array to state
• src/components/DownloadResult.tsx or a new ExportHistory.tsx

Acceptance criteria

• Export history is visible and lists up to 5 previous exports
• Clicking "Download" re-triggers the file download from the blob URL
• History is cleared on page reload (no persistence)
• Blob URLs are properly revoked when entries are cleared or evicted
• "Clear history" button works

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Screen Recording Required

Your PR for this issue must include a screen recording showing the feature working on your local machine (bun run dev → http://localhost:3000). PRs without a recording will not be merged.

See CONTRIBUTING.md for how to record.

[github-actions]

👋 Thanks for opening an issue, @magic-peach!

Our maintainers will review this shortly 🚀

Before you start working

• 📖 Read the CONTRIBUTING.md guide
• 💬 Wait for a maintainer to assign you the issue before starting work
• 🔍 Search for existing issues to avoid duplicates

For GSSoC'26 contributors

If you're contributing under GirlScript Summer of Code 2026, please mention it in your comment when requesting assignment:

"I'd like to work on this — contributing under GSSoC'26"

Architecture notes

Reframe is a static Next.js app with output: "export". Key points:

• All video processing uses FFmpeg.wasm (client-side, no server)
• headers() in next.config.ts won't work — use vercel.json instead
• not-found.tsx requires public/404.html + vercel.json routes config

Happy contributing! ⭐ Star the repo if you find it useful!

[github-actions]

Claude encountered an error —— View job

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I'll analyze this and get back to you.

[imuniqueshiv]

I'd like to work on this issue under GSSoC'26.

I can implement the export history panel with:

• in-memory export session tracking (max 5 entries)
• re-download support using stored blob URLs
• automatic blob URL cleanup on clear/eviction
• collapsible history UI with export metadata

I'll also include the required screen recording in the PR.

[imuniqueshiv]

/assign

[github-actions]

Hey @imuniqueshiv, this issue has been assigned to you! 🎉 Please make progress within 5 days or it will be automatically unassigned due to inactivity.