Fix reasoning_effort error for GPT-5.1/5.2 models in local mode (#317)

GPT-5.1 and GPT-5.2 reject reasoning_effort: "minimal" with error:
"Unsupported value: 'reasoning_effort' does not support 'minimal'".
Set reasoning_effort to "low" for these models to avoid the error.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: shrey150

stagehand/llm/client.py

@@ -114,6 +114,11 @@ async def create_response(
         if "gpt-5" in completion_model:
             filtered_params["temperature"] = 1
 
+            # GPT-5.1 and GPT-5.2 don't support "minimal" reasoning_effort.
+            # Set "low" for these models to avoid OpenAI API errors.
+            if "gpt-5.1" in completion_model or "gpt-5.2" in completion_model:
+                filtered_params["reasoning_effort"] = "low"
+
         self.logger.debug(
             f"Calling litellm.acompletion with model={completion_model} and params: {filtered_params}",
             category="llm",