fix(graph): dedupe the trailing message in the debug stream

Nodes after the trader do not append to messages, so the debug stream reprinted
the same trailing message once per node. Print it only when it changes; the
returned state is unchanged.

tradingagents/graph/trading_graph.py

@@ -381,11 +381,17 @@ class TradingAgentsGraph:
 
         if self.debug:
             trace = []
+            last_printed = None
             for chunk in self.graph.stream(init_agent_state, **args):
-                if len(chunk["messages"]) == 0:
-                    pass
-                else:
-                    chunk["messages"][-1].pretty_print()
+                if chunk["messages"]:
+                    msg = chunk["messages"][-1]
+                    # Nodes after the trader don't append to messages, so the
+                    # same trailing message repeats across chunks. Print it only
+                    # when it changes (#1027); the trace/state merge is unchanged.
+                    signature = (type(msg).__name__, getattr(msg, "content", None))
+                    if signature != last_printed:
+                        msg.pretty_print()
+                        last_printed = signature
                     trace.append(chunk)
             # Streamed chunks are per-node deltas. Merge them so the returned
             # state matches what graph.invoke() yields in the non-debug path.