Adds artifacts/api-server/tests/conversations-leave.test.mjs, modeled on
the existing apps-open.test.mjs, covering POST /conversations/:id/leave:
- Solo member leaving deletes the conversation entirely.
- Sole admin leaving with no successor auto-promotes the
earliest-joined remaining member.
- Sole admin leaving with a chosen successorId promotes that user.
- Sole admin leaving with a non-member successorId returns 400 and
leaves the group untouched (leaver still admin, no promotion).
- Non-admin leaving a group removes them with no admin promotion.
Tests create their own users (with the standard user role) and groups
directly in Postgres so joined_at ordering is deterministic for the
auto-promotion case, then exercise the route through HTTP using a real
session cookie obtained from POST /api/auth/login. An after() hook
cleans up all created conversations, participants, messages, role
assignments, and users.
The optional e2e for the chooser dialog is intentionally deferred and
proposed as follow-up #51.
Verified by running `pnpm --filter @workspace/api-server test` three
times consecutively; all 15 tests pass on every run.
Replit-Task-Id: e31c169d-a4f5-4387-a642-b39a422c1408
riyadhafraa
8fb6d54d78