-- Which arm of the skill-delivery A/B a mission ran.
--
-- 'inline'  — every pinned skill's body is appended to the turn prompt.
-- 'index'   — the prompt carries name + when_to_use + uri; the agent fetches
--             the bodies it judges relevant through the skills door.
--
-- Nullable, and NULL means 'inline'. Every mission that ran before this column
-- existed ran inline, so a default would be a claim about history that a NULL
-- correctly declines to make. `topology_exec::skill_delivery_mode` resolves
-- NULL, an unrecognised value and a missing row identically, to the arm that
-- requires nothing to be true.
--
-- Written once at launch by `mission_orchestrator`, which is the only place
-- that knows whether the skills door installed — 'index' is refused without
-- one, because an index the agent cannot fetch from is worse than no index.
ALTER TABLE missions ADD COLUMN IF NOT EXISTS skill_delivery TEXT;