Allow max OpenAI reasoning effort

llmcore.py

@@ -553,7 +553,7 @@ class BaseSession:
         def _enum(key, valid):
             v = cfg.get(key); v = None if v is None else str(v).strip().lower()
             return v if not v or v in valid else print(f"[WARN] Invalid {key} {v!r}, ignored.")
-        self.reasoning_effort = _enum('reasoning_effort', {'none', 'minimal', 'low', 'medium', 'high', 'xhigh'})
+        self.reasoning_effort = _enum('reasoning_effort', {'none', 'minimal', 'low', 'medium', 'high', 'xhigh', 'max'})
         self.service_tier = _enum('service_tier', {'auto', 'default', 'priority', 'flex'})
         self.thinking_type = _enum('thinking_type', {'adaptive', 'enabled', 'disabled'})
         self.thinking_budget_tokens = cfg.get('thinking_budget_tokens')