Fix Transformers 5 tied-weight save mapping

Keep the nested Qwen3-VL tied-weight target-to-source mapping as a dictionary so Transformers 5 can save the model and Sentence Transformers MultiVectorEncoder.

modeling_colqwen3.py

@@ -139,7 +139,10 @@ class ColQwen3(ColQwen3PreTrainedModel):
         )
         self.padding_side = getattr(config, "padding_side", "left")
         self.mask_non_image_embeddings = mask_non_image_embeddings
-        self._tied_weights_keys = [f"vlm.{k}" for k in (self.vlm._tied_weights_keys or [])]
+        inner_tied = self.vlm._tied_weights_keys or {}
+        self._tied_weights_keys = {
+            f"vlm.{target}": f"vlm.{source}" for target, source in inner_tied.items()
+        }
 
         self.post_init()