[Bugfix] Set separate CFG flag in Helios for CacheDiT (#3756)

Signed-off-by: Alex Brooks <albrooks@redhat.com>

tests/diffusion/cache/test_cache_dit.py

@@ -16,6 +16,7 @@ pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
 
 SEPARATE_CFG_ENABLERS = [
     cd_backend.enable_cache_for_ltx2,
+    cd_backend.enable_cache_for_helios,
     cd_backend.enable_cache_for_wan22,
     cd_backend.enable_cache_for_longcat_image,
 ]

vllm_omni/diffusion/cache/cache_dit_backend.py

@@ -1413,7 +1413,7 @@ def enable_cache_for_helios(pipeline: Any, cache_config: Any) -> Callable[[int],
             params_modifiers=[
                 ParamsModifier(cache_config=db_cache_config, calibrator_config=calibrator_config),
             ],
-            has_separate_cfg=False,
+            has_separate_cfg=True,
         ),
         cache_config=db_cache_config,
         calibrator_config=calibrator_config,