Revise and expand the authoritative .chord format specification:
version bump 1.0 → 2.0, clarified period scope, updated tokenization
rules, grammar tables, and key normalization details.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Authoritative .chord file format spec covering header fields, body
syntax, chord symbol grammar, tokenization rules, and key normalization.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>