docs: compress recognition demo GIFs at 30 fps

[SakuraMathcraft]

Summary

Re-encode the three README demo GIFs from the original MP4 recordings at 720x405, approximately 30 fps, original playback speed, and a 128-color palette. Keep GIF presentation and existing README paths; do not switch to video players.

Demo	Before	After
Screenshot	12,974,595 bytes	8,592,845 bytes
Image	13,475,519 bytes	8,572,467 bytes
PDF	14,547,878 bytes	9,454,715 bytes

Total decreases from approximately 41 MB to 27 MB; each file is below 10 MB.

Validation

• ffprobe verified 720x405 dimensions, frame counts, and preserved durations.
• Extracted-frame visual check performed during preparation.
• git diff --check passed.
• Only three GIF assets change; no application code or README text changes.
• GitHub page loading still needs verification after merge; smaller size alone is not proof that every network/rendering issue is resolved.