test(host_agent): both sensor refreshes run in one event loop (#5786)

The second asyncio.run got a pooled connection bound to the first loop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/integration/test_host_metrics.py

@@ -206,18 +206,16 @@ def test_sensors_are_judged_from_raw_hours_and_rollups_together(app):
                                                    recorded_at=at.replace(minute=m)))
                     s.add(PluginMetricLatest(source_module="host_agent", resource_name=res,
                                              metric_name="temp_c", value=f(99), recorded_at=now))
-            return await sensors.refresh(s, now)
+            first = await sensors.refresh(s, now)
+            read_from = sensors._read_from
+            # The next hour reads only the hour the last read ended in; one
+            # event loop, since the engine's pooled connections belong to it.
+            return first, read_from, await sensors.refresh(s, now + timedelta(hours=1))
 
     sensors._hours.clear()
     sensors._read_from = None
-    got = asyncio.run(_go())
+    got, read_from, again = asyncio.run(_go())
     assert list(got[host]) == ["SYSTIN"]
     assert got[host]["SYSTIN"].startswith("falls as the CPU warms (r -1.00 over 100 h")
-
-    async def _again():                        # the next hour reads only the hour it ended in
-        async with app.db_sessionmaker() as s:
-            return await sensors.refresh(s, now + timedelta(hours=1))
-
-    assert sensors._read_from == now.replace(minute=0)
-    again = asyncio.run(_again())
+    assert read_from == now.replace(minute=0)
     assert again[host]["SYSTIN"].startswith("falls as the CPU warms (r -1.00 over 100 h")