Add pipeline tag

This PR adds the `pipeline_tag` to the model card metadata, making the model discoverable under the unconditional image generation category on the Hugging Face Hub. No other changes are made.

README.md

@@ -1,9 +1,10 @@
 ---
 tags:
-  - pytorch
-  - pathology
-  - flow-matching
-  - dit
+- pytorch
+- pathology
+- flow-matching
+- dit
+pipeline_tag: unconditional-image-generation
 ---
 
 This model provides the **pretrained DiT backbone for Agent-GenPath**, supporting pathology image synthesis and downstream segmentation.
@@ -28,4 +29,4 @@ Code: [**https://github.com/script-Yang/Agent-GenPath**](https://github.com/scri
       primaryClass={cs.CV},
       url={https://arxiv.org/abs/2611.06701},
 }
-```
+```