test(snmp): the poll test reaches the plugin as the app loaded it (milestone 491)

SNMP is on by default, so the loader has already mapped snmp_devices under
_steward_plugin_snmp; importing plugins.snmp.models defined the table twice
(integration lane, run 8788).

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

tests/integration/test_snmp_poll.py

@@ -4,6 +4,7 @@ Requires STEWARD_DATABASE_URL."""
 from __future__ import annotations
 
 import asyncio
+import importlib
 import os
 import uuid
 
@@ -20,14 +21,24 @@ def app():
     return create_app(testing=False)
 
 
+def _snmp(sub):
+    """A submodule of the snmp plugin as the app loaded it: it is on by
+    default, so its models are already mapped under the loader's name, and
+    importing plugins.snmp.models would define the table a second time."""
+    from steward.core.plugin_manager import get_loaded_plugin_modules
+    loaded = get_loaded_plugin_modules().get("snmp")
+    return importlib.import_module(f"{loaded.__name__ if loaded else 'plugins.snmp'}.{sub}")
+
+
 def test_a_poll_records_why_a_device_is_silent_and_what_another_answered(app):
     from sqlalchemy import select
 
-    from plugins.snmp import scheduler
-    from plugins.snmp.models import SnmpDevice
-    from plugins.snmp.poller import PollResult
     from steward.models.metrics import PluginMetricLatest
 
+    scheduler = _snmp("scheduler")
+    SnmpDevice = _snmp("models").SnmpDevice
+    PollResult = _snmp("poller").PollResult
+
     tag = uuid.uuid4().hex[:8]
     up, down = f"sw-{tag}", f"ups-{tag}"
     counts = iter([1_000.0, 61_000.0])