Add {start_of_notes}/{end_of_notes} (and short forms {son}/{eon}) block
directives to ChordProParser for multi-paragraph note content. Blank lines
within the block separate paragraphs. The renderer now word-wraps note
paragraphs to fit within the content width. MeasurementEngine estimates
wrapped line count for more accurate height calculations.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
