One-time script (dry-run default, --apply in a transaction, idempotent) mapping a
flat roof's stated depth (flat: Nmm) onto the nearest Table 16 rung member so the
overlay scores it by thickness, not the age-band default. Updates property_overrides
(TEXT) immediately; the roof_type pgEnum cache writes are deferred until the FE adds
the FLAT_*MM members. Dry-run against the audited DB reports 102 rows, deferring
Flat 50/100/150 mm.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>