[Model] [Config] Correctly identify granite-4.0-micro as non-hybrid model (#28563)

Signed-off-by: Thomas Parnell <tpa@zurich.ibm.com>

vllm/config/model.py

@@ -1619,6 +1619,13 @@ class ModelConfig:
 
     @property
     def is_hybrid(self) -> bool:
+        # Handle granite-4.0-micro case which uses hybrid config but does not
+        # actually contain any non-attention layers.
+        layer_types = getattr(self.hf_config, "layer_types", None)
+        if layer_types is not None and all(
+            layer == "attention" for layer in layer_types
+        ):
+            return False
         return self._model_info.is_hybrid
 
     @property