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/graph/trading_graph.py

@@ -116,7 +116,9 @@ class TradingAgentsGraph:
             self.conditional_logic,
         )
 
-        self.propagator = Propagator()
+        self.propagator = Propagator(
+            max_recur_limit=self.config.get("max_recur_limit", 100),
+        )
         self.reflector = Reflector(self.quick_thinking_llm)
         self.signal_processor = SignalProcessor(self.quick_thinking_llm)