Restored the stable 1.0.3 download behavior after regressions were observed in the later review-cleanup build.

This release keeps the proven YouTube and Loom download paths intact:
- YouTube high-quality downloads work through the local helper flow.
- Loom videos are captured in real time and saved as seekable WebM files.
- The popup no longer waits on YouTube metadata warming before allowing downloads to proceed.

No data is collected by the extension.

This update improves the Firefox add-on packaging and removes Mozilla validation warnings while keeping the download behavior unchanged.

Fixed the release packaging so the source archive now includes only the actual source files and excludes temporary build/test artifacts, large captured media files, and other generated files.
Removed legacy compatibility code from the bundled EBML vendor library that triggered Mozilla validation warnings.
The add-on’s core video detection, HLS/DASH handling, YouTube support, Loom capture path, and download behavior remain the same.

Improved YouTube downloads in this release, and transfer the language to English/

• Better reliability for YouTube downloads, with improved handling for high-quality MP4 output.
• Improved audio handling and playback compatibility for downloaded YouTube videos.
• Faster YouTube download startup and no extra YouTube tab opening during download.
  *Added clearer guidance in the popup when the highest-quality YouTube option may create a large file, with a suggestion to use + for a slightly smaller version.
• General stability and UI improvements for grouped video variants.
  *Transfer the language to full English