-- 0011_session_persona down: drop the role-binding columns added by the up
-- migration. SQLite DROP COLUMN (3.35+) is already relied on by 0006/0007/0009/0010,
-- and neither column is referenced by an index, view or constraint, so a plain drop
-- is safe. The rolled-back state is the pre-multi-character one: a session belongs
-- to no explicit role and every row resolves to the global default role
-- (persona_id = '' is itself the "inherit the default" value, so the dropped data
-- only ever held explicit non-default bindings — the code was the only consumer).

ALTER TABLE chat_messages DROP COLUMN persona_id;

ALTER TABLE chat_sessions DROP COLUMN persona_id;