Update LPi4A test report to 20251226

[EnzoDing-rgb]

Summary

• Update LPi4A RevyOS test report to RevyOS 20251226.
• Refresh download links to the 20251226/ directory and use the exact artifact filenames.
• Update fastboot flashing commands to match the new u-boot/boot/root images.
• Replace screencast embed with the new asciinema recording: 845060.
• Update screenshot reference to the new local image file: B.png.
• Align both English and Chinese READMEs to the reference template structure (headings, wording, section order).
• Fix .gitignore rules for reference files and stop tracking README_en_ref.md in git.