* fix(review): serialize concurrent triggers per worker to stop double-spawn
Engine.Trigger was a read-then-write (idempotency check -> reviewer spawn ->
InsertReviewRun) with no serialization and no backing constraint. Two near-
simultaneous triggers for the same worker at the same head SHA both passed the
GetReviewRunBySessionAndSHA check, both spawned a reviewer against the same
deterministic review-<id> handle, and both inserted a running run for one commit.
Add a per-worker keyed mutex (lockWorker) held across the whole Trigger body, so
the loser re-reads the freshly-recorded run and short-circuits to Created:false
instead of spawning. Back it with a partial unique index on
review_run(session_id, target_sha) (migration 0013) as a cross-restart safety
net; rows with an empty target_sha (head not yet observed) are excluded so they
are not blocked.
Adds a concurrency test asserting N simultaneous triggers spawn once and record
one run.
Closes#242
* fix(review): make migration 0013 dedup-safe and handle the unique conflict in Trigger
Pre-#242 daemons can already hold duplicate (session_id, target_sha)
review_run rows, on which CREATE UNIQUE INDEX fails and wedges startup.
Migration 0013 now collapses each duplicate group to a single survivor
(a completed pass over a still-running one, then newest by created_at)
before building the index.
Trigger now treats a unique-constraint hit as a fallback rather than an
error: InsertReviewRun maps it to the new domain.ErrDuplicateReviewRun
sentinel, and Trigger re-reads GetReviewRunBySessionAndSHA and returns
that run with Created:false instead of surfacing a raw error after the
reviewer may already have launched.
96d1649e46