-- §6.6: per-RFC model availability. The frontmatter field is
-- optional; NULL in this column means absent (inherit the operator
-- universe), '[]' means explicit opt-out, '[...]' is the populated
-- list. The distinction is load-bearing — we cannot collapse to a
-- NOT NULL DEFAULT '[]' the way the other *_json columns do.

ALTER TABLE cached_rfcs ADD COLUMN models_json TEXT;