[None][fix] AutoDeploy: set enable_spec_decode on ADEngine for disagg (#15260)

Signed-off-by: Shixiaowei02 <39303645+Shixiaowei02@users.noreply.github.com>
Co-authored-by: gramnarayan <105831528+govind-ramnarayan@users.noreply.github.com>

Author: Shixiaowei02

tensorrt_llm/_torch/auto_deploy/shim/ad_executor.py

@@ -494,6 +494,11 @@ def __init__(
         else:
             self.max_total_draft_tokens = 0
 
+        # ADEngine skips PyTorchModelEngine.__init__, so set the spec-decode
+        # flags that shared PyExecutor code expects on a ModelEngine.
+        self.is_spec_decode = self.spec_config is not None
+        self.enable_spec_decode = self.is_spec_decode
+
         # For compatibility with PyTorchModelEngine utilities
         self.batch_size = cache_seq_interface.info.max_batch_size