-- Call participants: one call log per real conversation, with a list of
-- everyone who was actually ON it (original agent + any warm-transfer
-- target agents + any PSTN parties added to the conference). Supervisor
-- listen/whisper/barge legs are deliberately NOT calls at all (the
-- tracker drops their events entirely) so they never appear here.
--
-- A JSON array column rather than a child table: it's display-only
-- metadata that rides the existing one-row-per-linkedid upsert, never
-- queried/joined on its own. Shape: [{ "type":"agent"|"pstn",
-- "userId":<uuid|null>, "name":<string>, "extension":<string|null>,
-- "number":<string|null> }].
ALTER TABLE calls ADD COLUMN IF NOT EXISTS participants_json TEXT NULL AFTER notes;