fix(agents): carry the Portfolio Manager's rating through the run (#1383)

- the typed rating is the state's final_rating; propagate returns it, and the memory log tag, the state log and the CLI review check read it
- the decision text is parsed only when the Portfolio Manager answered in free text
- TradingAgentsGraph.process_signal is removed

tests/test_memory_log.py

@@ -898,6 +898,7 @@ class TestLegacyRemoval:
 
         fake_state = {
             "final_trade_decision": "Rating: Buy\nBuy NVDA.",
+            "final_rating": "Buy",
             "company_of_interest": "NVDA",
             "trade_date": "2026-01-10",
             "market_report": "",
@@ -924,7 +925,6 @@ class TestLegacyRemoval:
         mock_graph.graph.invoke.return_value = fake_state
         mock_graph.propagator.create_initial_state.return_value = fake_state
         mock_graph.propagator.get_graph_args.return_value = {}
-        mock_graph.process_signal.return_value = "Buy"
         # Bind the real _run_graph so propagate's call to self._run_graph executes
         # the actual write path instead of the auto-MagicMock.
         mock_graph._run_graph = functools.partial(