refactor(gateway): ponytail F2 - drop dead metadata, unreachable variant fallback, redundant except member

ingestor/adapters/nats_consumer.py

@@ -39,7 +39,7 @@ class NatsWriteConsumer:
     async def _handle(self, msg) -> None:
         try:
             payload = json.loads(msg.data)
-        except (ValueError, UnicodeDecodeError) as e:
+        except ValueError as e:  # includes JSONDecodeError and UnicodeDecodeError
             preview = msg.data[:200]
             self.logger.error(f'NatsWriteConsumer dropped malformed JSON ({e}): {preview!r}')
             return

ingestor/engines/write.py

@@ -64,14 +64,12 @@ class WriteEngine(SientiaMonitoring):
         logger: Logger,
         notification_handler: NotificationHandler,
         metrics_controller: MetricsController,
-        metadata: dict | None = None,
         write_timestamp: bool = True,
         write_quality: bool = True,
         min_pause_s: float = 0.0,
     ):
         self.pool = pool
         self.sink = sink
-        self.metadata = metadata or {}
         self.write_timestamp = write_timestamp
         self.write_quality = write_quality
         self.min_pause_s = min_pause_s
@@ -130,7 +128,8 @@ class WriteEngine(SientiaMonitoring):
         }
 
     def _variant_type(self, data_type: str) -> ua.VariantType:
-        return _VARIANT_TYPES.get(data_type.strip().lower(), ua.VariantType.String)
+        # direct index: unknown dtypes already became ConversionError in to_typed_value
+        return _VARIANT_TYPES[data_type.strip().lower()]
 
     def _build_datavalue(self, cmd: dict, typed_value) -> ua.DataValue:
         variant = ua.Variant(typed_value, self._variant_type(cmd['data_type']))