Harden live material polling state

src/production_analytics/service/material_polling.py

@@ -65,8 +65,10 @@ class MaterialPollingService:
         )
 
     def poll_once(self, *, now: datetime) -> MaterialPollResult | None:
+        if now.tzinfo is None or now.utcoffset() is None:
+            raise ValueError("now must be timezone-aware")
         run = self._gateway.get_open_production_run(self._machine_id)
-        if run is None:
+        if run is None or now < run.start:
             return None
 
         saved_polling_state = self._state_store.load(
@@ -92,6 +94,9 @@ class MaterialPollingService:
             )
             start = run.start
 
+        if now < start:
+            return None
+
         integrator = MaterialConsumptionIntegrator(
             self._config,
             initial_state=initial_state,