feat(encoder): add multi-format support with mp3, aac, and opus presets

[flexiondotorg]

• Introduce formatPreset type mapping each format to its codec, bitrate, sample rate, muxer, and extension
• Support --format flag (mp3, aac, opus) with mp3 as default
• MP3: CBR 112/192kbps, 44.1kHz, LAME quality 3, 20.5kHz lowpass, ID3v2.4 tags with cover art
• AAC: CBR 64/128kbps, 44.1kHz, iTunes MP4 atoms with cover art, .m4a extension
• Opus: VBR ~32/~48kbps, 48kHz, Vorbis comments (text only), .opus extension
• Update filename generation to use format-specific extensions instead of hardcoded .mp3
• Remove obsolete ID3v2 writer library; use FFmpeg muxer-native tagging for all formats
• Add encoder tests covering each format's preset configuration
• Update documentation and CLI reference for multi-format output
• Add .tailor.yml configuration for linting and static analysis
• Refactor command-line interface to show Ready to encode message with format name

Closes #9

[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

<sub>Requires human review: This PR introduces multi-format support with new encoding presets, replaces the ID3 tag writer with FFmpeg muxer-native tagging, and modifies the core encoder pipeline, which are significant changes to critical business logic that require human review to ensure correctness and avoid regressions.

Re-trigger cubic</sub>