fix(llm): forward reasoning effort to GPT-6 and gate minimal thinking

- reasoning_effort was forwarded only to IDs matching gpt-5 or the o-series, so
  GPT-6 models silently dropped the configured effort; match GPT-5 and later,
  with a version boundary so unrelated IDs do not match
- Gemini Pro, 3.8+ and the -latest aliases reject thinking_level "minimal"
  with a 400; send it only to numbered Flash models before 3.8 and map it to
  "low" elsewhere, since aliases move between generations

tradingagents/llm_clients/openai_client.py

@@ -168,11 +168,11 @@ _PASSTHROUGH_KWARGS = (
     "api_key", "callbacks", "http_client", "http_async_client",
 )
 
-# OpenAI's ``reasoning_effort`` is only accepted by reasoning models — the GPT-5
-# family and the o-series. Non-reasoning models (gpt-4.1, gpt-4o, ...) 400 with
+# OpenAI's ``reasoning_effort`` is only accepted by reasoning models — GPT-5 and
+# later, and the o-series. Non-reasoning models (gpt-4.1, gpt-4o, ...) 400 with
 # "Unsupported parameter: 'reasoning.effort' is not supported with this model".
 # Drop the kwarg for those rather than crash the run.
-_OPENAI_REASONING_MODEL = re.compile(r"^(gpt-5|o[1-9])")
+_OPENAI_REASONING_MODEL = re.compile(r"^(?:gpt-(?:[5-9]|[1-9]\d)|o[1-9])(?:[.-]|$)")
 
 
 def _supports_reasoning_effort(model: str) -> bool: