refractor(baby_client): remove hard-coded bf

src/aliby/baby_client.py

@@ -143,7 +143,7 @@ class BabyRunner:
         )
         self.brain = BabyBrain(**self.model_config)
         self.crawler = BabyCrawler(self.brain)
-        self.bf_channel = self.tiler.get_channel_index("Brightfield")
+        self.bf_channel = self.tiler.ref_channel_index
 
     @classmethod
     def from_tiler(cls, parameters: BabyParameters, tiler):

src/aliby/tile/tiler.py

@@ -548,6 +548,10 @@ class Tiler(ProcessABC):
             )
         return np.stack(res, axis=1)
 
+    @property
+    def ref_channel_index(self):
+        return self.get_channel_index(self.parameters.ref_channel)
+
     def get_channel_index(self, item):
         """
         Find index for channel using regex. Returns the first matched string.