[BUG] show original video alongside processed preview in comparison mode

[kunal-yelgate]

Bug description
The comparison mode currently displays the processed preview in both panes, which prevents users from seeing how the exported result differs from the original uploaded video. This makes the comparison feature less effective for evaluating framing and aspect ratio changes before export.

Steps to reproduce
Steps to reproduce the behavior:

1. Go to the Reframe editor.
2. Upload a video.
3. Change the aspect ratio or fit/fill settings.
4. Open the Comparison view.
5. Observe that both panes display the same processed output.

Expected behavior
One pane should display the original, unmodified video, while the other displays the processed preview reflecting the current editor settings. This should allow users to compare the original and edited versions side by side in real time.

Actual behavior
Both panes display the processed preview, making it difficult to identify the differences between the original video and the final output.

[github-actions]

👋 Thanks for opening an issue, @kunal-yelgate!

Our maintainers will review this shortly 🚀

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• 📖 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!

[kunal-yelgate]

add gssoc26 label