-- Bind a research topic to a workspace repo + the on-disk path where
-- `start_topic` clones a working copy. Both nullable so pre-existing
-- topics don't need backfill and topics without a repo still work.
--
--   repo_id — the repo the user picked in the wizard. ON DELETE SET
--     NULL so removing the connection doesn't cascade-nuke the topic.
--
--   repo_workspace_path — absolute path on the API host where
--     `start_topic` executed `git clone --depth 1`. Set once when the
--     clone succeeds; a subsequent start can reuse it (skip re-clone).
--     Feeds the coordinator prompt so agents know where the files live.

ALTER TABLE research_topics
    ADD COLUMN repo_id UUID REFERENCES repos (id) ON DELETE SET NULL,
    ADD COLUMN repo_workspace_path TEXT;

CREATE INDEX research_topics_repo_idx
    ON research_topics (repo_id)
    WHERE repo_id IS NOT NULL;