- Create shared/media/format_utils.py with format detection and validation
- Create shared/media/video_encoder.py with FFmpegEncoder and PILEncoder classes
- Extract validate_video_for_discord to shared utility
- Extract ffmpeg detection to shared detect_ffmpeg() function
- Extract Discord video optimization to shared optimize_video_for_discord()
- Remove duplicate code from video_node.py (-109 lines)
Phase 3 summary:
- video_node.py: 1201 -> 1092 lines (9% reduction this phase)
- Total reduction from original: 1562 -> 1092 lines (30% reduction)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
