fix(protocol): reduce HTTP 400 errors for replay — accept tool_choice=none + extra fields

1. tool_choice='none' now accepted per OpenAI spec (strip and continue).
   Previously raised ValueError, causing 400 on replay requests.

2. Pydantic extra='forbid' → extra='ignore'. Real-world replay requests
   from Tencent API contain fields like service_tier, store, metadata,
   reasoning_effort etc. that our model doesn't declare. forbid rejects
   them all; ignore silently drops them.

Sub 168 had 77 http_400 errors in replay — these two fixes should
eliminate most of them, improving successful request count and score.

CCCL tuning_transform.cuh pattern: accept all valid input configurations
gracefully (policy_selector handles unknown cc values with fallback).

qwen3_6_scripts/protocol.py

@@ -57,7 +57,10 @@ class CustomChatCompletionMessageParam(TypedDict, total=False):
 
 class OpenAIBaseModel(BaseModel):
     # OpenAI API does not allow extra fields
-    model_config = ConfigDict(extra="forbid")
+    # Real-world clients (replay, third-party SDKs) may send extra fields
+    # like service_tier, store, metadata, reasoning_effort, etc.
+    # "ignore" accepts the request and silently drops unknown fields.
+    model_config = ConfigDict(extra="ignore")
 
 
 class ErrorResponse(OpenAIBaseModel):
@@ -517,6 +520,12 @@ class ChatCompletionRequest(OpenAIBaseModel):
         # if "tool_choice" is specified -- validation
         if "tool_choice" in data:
 
+            # "none" means don't use any tools — valid per OpenAI spec,
+            # just strip tool_choice and let vLLM ignore tools.
+            if data["tool_choice"] == "none":
+                del data["tool_choice"]
+                return data
+
             # ensure that if "tool choice" is specified, tools are present
             if "tools" not in data or data["tools"] is None:
                 raise ValueError(