chore: annotate headroom pre-call hook dict for the type-discipline budget

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/proxy/guardrails/guardrail_hooks/headroom/headroom.py

@@ -728,7 +728,11 @@ class HeadroomGuardrail(CustomGuardrail):
             return None
         if not has_headroom_retrieve_tool(kwargs.get("tools")):
             return None
-        return {**kwargs, "stream": False, HEADROOM_CONVERTED_STREAM_KEY: True}
+        return {  # mutable-ok: the hook contract is a plain dict the router merges into the request kwargs
+            **kwargs,
+            "stream": False,
+            HEADROOM_CONVERTED_STREAM_KEY: True,
+        }
 
     async def async_should_run_agentic_loop(
         self,