The host/last_seen fields added in ba5ee66 left mis-indented struct
literals in scheduler.rs tests and a cramped match arm in socket.rs.
cargo fmt --all (no runner in CI catches this; see quality-gates.md).
(Sam & Claude)
The Phase 3 landing (host/last_seen/heartbeat/migrations) shipped with
zero test coverage — test_agent_registry only registered with host=None
and never exercised the new surface. Add 5 tests:
- register_agent persists host + stamps last_seen
- heartbeat advances last_seen and preserves host via COALESCE (None)
- heartbeat(Some(host)) updates host in place
- heartbeat on unknown agent id fails closed (StoreError::NotFound)
- run_migrations idempotent across store reopen (file-based; the ALTER
statements must not raise "duplicate column name" on the second open)
Store crate: 11 -> 16 tests, all green.
(Sam & Claude)
