fix(pico-sensor): disconnect mqtt client before testing publish

pico-sensor/src/tests/test_mqtt_client.c

@@ -38,6 +38,7 @@ void test_MqttClient_Publish_Disabled(void) {
 
 // Test that publishing fails with ERR_FAILED if not connected, even if publishing is enabled
 void test_MqttClient_Publish_NotConnected(void) {
+    MqttClient_Disconnect(); // Ensure we are not connected
     MqttClient_SetDoPublish(true);
     int res = MqttClient_Publish((const unsigned char*)"test/topic", (const unsigned char*)"value");
     TEST_ASSERT_EQUAL_INT_MESSAGE(ERR_FAILED, res, "Publish should fail with ERR_FAILED if not connected");