Init Gemma in float32, users control dtype via torch_dtype param

modeling_slip.py

@@ -433,6 +433,7 @@ class Gemma3MultimodalModel(nn.Module):
                 model_id, trust_remote_code=True)
         else:
             config = AutoConfig.from_pretrained(model_id, trust_remote_code=True)
+            config.torch_dtype = torch.float32
             self.model = AutoModelForCausalLM.from_config(
                 config, trust_remote_code=True)