Add metadata_labels ("abbreviated"/"german") and metadata_position
("top"/"bottom") options to LayoutConfig. German labels use "Worte:" and
"Weise:" instead of "T:" and "M:", with "Worte und Weise:" when lyricist
and composer are the same person. Metadata at bottom position renders
after notes with word-wrapping. MeasurementEngine accounts for two-line
metadata in German label mode.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>