feat: Yahoo Finance SSH proxy + Xiaomi MiMo LLM support

- Add SSH proxy via foreign server for Yahoo Finance bypass
- Add fallback in load_ohlcv and get_YFin_data_online
- Add LLM JSON decode retry (3 attempts) in NormalizedChatOpenAI
- Add yahoo_proxy.py utility module
- Add test_smoke.py and patches/

tradingagents/llm_clients/openai_client.py

@@ -33,7 +33,21 @@ class NormalizedChatOpenAI(ChatOpenAI):
     """
 
     def invoke(self, input, config=None, **kwargs):
-        return normalize_content(super().invoke(input, config, **kwargs))
+        import json as _json
+        import time as _time
+        import logging as _logging
+        _logger = _logging.getLogger(__name__)
+        max_retries = 3
+        for attempt in range(max_retries):
+            try:
+                return normalize_content(super().invoke(input, config, **kwargs))
+            except (_json.JSONDecodeError, Exception) as e:
+                if 'JSONDecodeError' in type(e).__name__ or 'Expecting value' in str(e):
+                    if attempt < max_retries - 1:
+                        _logger.warning(f"LLM returned invalid JSON, retrying ({attempt+1}/{max_retries}): {e}")
+                        _time.sleep(2 * (attempt + 1))
+                        continue
+                raise
 
     def with_structured_output(self, schema, *, method=None, **kwargs):
         caps = get_capabilities(self.model_name)