Applies loudness normalization (default target -14 LUFS, common streaming-platform standard) plus a peak limiter to an already-generated production.
The user wants a "radio-ready" or streaming-normalized version of a track they've already generated.
mcp__cogmusic__master({ id: "<production-id>" }).lufs_before and lufs_after — report both so the user can see the actual loudness change, not just "done."music-productions (if one exists) with the new lufs_before/lufs_after/has_mastered: true fields so later lookups don't need a round-trip.