fix: bundle config/recursion/missing-key fixes

- dataflows/config: deepcopy + one-level dict merge so a partial
  set_config doesn't clobber sibling defaults
- graph: thread max_recur_limit from config to Propagator
- openai_client: name the missing env var in the API-key error

#788 #764 #680

tradingagents/dataflows/config.py

@@ -1,6 +1,8 @@
-import tradingagents.default_config as default_config
+from copy import deepcopy
 from typing import Dict, Optional
 
+import tradingagents.default_config as default_config
+
 # Use default config but allow it to be overridden
 _config: Optional[Dict] = None
 
@@ -9,22 +11,31 @@ def initialize_config():
     """Initialize the configuration with default values."""
     global _config
     if _config is None:
-        _config = default_config.DEFAULT_CONFIG.copy()
+        _config = deepcopy(default_config.DEFAULT_CONFIG)
 
 
 def set_config(config: Dict):
-    """Update the configuration with custom values."""
+    """Update the configuration with custom values.
+
+    Dict-valued keys (e.g. ``data_vendors``) are merged one level deep so a
+    partial update like ``{"data_vendors": {"core_stock_apis": "alpha_vantage"}}``
+    keeps the other nested keys from the default; scalar keys are replaced.
+    """
     global _config
-    if _config is None:
-        _config = default_config.DEFAULT_CONFIG.copy()
-    _config.update(config)
+    initialize_config()
+    incoming = deepcopy(config)
+    for key, value in incoming.items():
+        if isinstance(value, dict) and isinstance(_config.get(key), dict):
+            _config[key].update(value)
+        else:
+            _config[key] = value
 
 
 def get_config() -> Dict:
     """Get the current configuration."""
     if _config is None:
         initialize_config()
-    return _config.copy()
+    return deepcopy(_config)
 
 
 # Initialize with default config