fix: update watchdog test for 5 checks including Kimi Heartbeat (closes #1512)

run_health_checks() returns 5 checks (added check_kimi_heartbeat()),
but test expected 4. Updated test to expect 5 and verify Kimi Heartbeat
is present.

tests/test_nexus_watchdog.py

@@ -303,9 +303,10 @@ class TestRunHealthChecks:
                 heartbeat_path=tmp_path / "missing.json",
             )
 
-        assert len(report.checks) == 4
+        assert len(report.checks) == 5
         check_names = {c.name for c in report.checks}
         assert "WebSocket Gateway" in check_names
         assert "Consciousness Loop" in check_names
         assert "Heartbeat" in check_names
         assert "Syntax Health" in check_names
+        assert "Kimi Heartbeat" in check_names