The drift-register taxonomy is documented in `drift/README.md` but the register itself is empty. Two inter-standard divergences are already written as prose inside crosswalk `notes` blocks (`rent_amount`, `market_rent`). **What:** Promote those two divergences into standalone structured register entries following the documented taxonomy. **Deliverables:** - One register file per divergence (or one file with both), classified per the taxonomy categories - Standards + versions involved, precise location of divergence, and the classification - Cross-link back to the originating crosswalk `notes` **Why:** Turns existing prose into the structured register the README promises. Natural precursor to a JSON Schema gate for these files. **Scope:** ~1 hour.