The landlord property-type description is a "<dwelling type>: <built form>: <floor>"
split whose leading token IS the dwelling type; the built-form tail is not. The
LLM occasionally over-read the tail and flipped the type — a handful of
"Bungalow: EndTerrace" / "Bungalow: MidTerrace" dwellings were stored as House.
Adds property_type_guard (claims the recognised leading token: House / Bungalow /
Flat / Maisonette / Park home; defers unrecognised phrasings to the LLM) and wires
property_type through a GuardedColumnClassifier, so the built-form tail can never
flip the type and the live path is deterministic.
Applied the scoped backfill to portfolio 796 (Hyde): 3 rows corrected from House
back to Bungalow. No enum migration needed — the targets are original members.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
