One-time script (dry-run default, --apply in a transaction, idempotent) reusing the
live glazing_mix_guard so the backfill and classifier cannot drift. Maps every
genuine percentage-mix override (neither type >= 90%) off a flattened single type
onto MIXED (no overlay -> the cert's per-window glazing is kept). property_overrides
TEXT updated now; the glazing pgEnum cache write for 'Mixed glazing' is deferred
until the FE adds the member. Dry-run against the audited DB reports 647 rows.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
