[LFM2-VL] Add DSpark speculative decoding (#40651)

python/sglang/srt/models/lfm2_vl.py

@@ -180,6 +180,14 @@ class Lfm2VlForConditionalGeneration(nn.Module):
     def get_input_embeddings(self) -> nn.Embedding:
         return self.language_model.model.embed_tokens
 
+    @property
+    def lm_head(self):
+        return self.language_model.lm_head
+
+    def set_dflash_layers_to_capture(self, layer_ids: List[int]):
+        # Lfm2ForCausalLM applies the HF-layer-k -> "before layer k+1" shift.
+        self.language_model.set_dflash_layers_to_capture(layer_ids)
+
     def get_image_feature(self, items: List[MultimodalDataItem]) -> torch.Tensor:
         """Process images through vision tower and projector.