The one-time legacy normalize migration finished; NormalizeProject had no
production callers. Delete migrate.go, the 26 *_migrate.go files, the
importLegacyItempropsRegistry cluster, loadLegacyTLK, and the 48 test
blocks that only exercised them. mergeLegacyTLK moves to tlk_native.go
because the live TLK compiler still uses it for base_dialog.json.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>