feat: implement high-quality GIF export using two-pass FFmpeg pipeline

[Vagventure]

Description

This PR introduces GIF export support to Reframe via a two-pass FFmpeg pipeline for accurate colour mapping, along with a GIF-aware size estimator and UI updates across the export panel and format selector.

Changes Made

• src/lib/types.ts: Added "gif" to the format union in both EditRecipe and ExportResult. Previously ExportResult was missing "gif" despite EditRecipe already declaring it, which would have caused a TypeScript error on return.

• src/lib/ffmpeg.ts:

  • Added "gif" case to getOutputConfig, returning .gif / image/gif.
  • Widened the format parameter of buildArguments to include "gif" for type safety.
  • Added paletteName (palette_<sessionId>.png) to cleanupFiles so the temporary palette is always deleted after export.
  • Inserted a two-pass GIF branch that runs before the standard MP4/WebM exec flow and returns early, keeping GIF fully isolated from the fallback/retry logic:
    • Pass 1 — runs palettegen through the existing buildVideoFilter output so all transforms (trim, scale, rotate, speed, colour corrections) are respected.
    • Pass 2 — applies paletteuse via -lavfi using the generated palette, producing a high-quality GIF with accurate colour mapping.

• src/components/FormatSelector.tsx: Added "gif" to FORMAT_OPTIONS, changed the button grid from grid-cols-3 to grid-cols-4, and widened the onChange type cast to include "gif".

• src/components/ExportSettings.tsx:

  • Derived isGif boolean from recipe.format === "gif".
  • Added a conditional amber warning below the estimated size when GIF is selected, advising users to keep clips under 10 seconds.
  • Hid the "Sound on completion" toggle when GIF is active (GIF carries no audio).

Related Issue

Closes #658

Type of Contribution

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

Participant Info

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

Screen Recording

Recording / Loom link:

reframe_1920x1080.2.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 (no ESLint errors)
• bunx tsc --noEmit passes (no TypeScript errors)
• 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 (required for UI/feature/design changes)

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[github-actions]

👋 Thanks for your PR, @Vagventure!

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

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

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Happy coding! 🎉

[github-actions]

✅ PR Format Check Passed — @Vagventure

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