refactor: move the decision log to tradingagents/decision_log.py

- it is the run's persistent record, used by the graph, backtest and CLI, not an agent utility; agents/utils is gone

tradingagents/backtest.py

@@ -22,9 +22,9 @@ from datetime import datetime, timedelta
 from pathlib import Path
 
 from tradingagents.agents.rating import RATING_REVIEW
-from tradingagents.agents.utils.memory import TradingMemoryLog
 from tradingagents.dataflows.date_window import get_current_date
 from tradingagents.dataflows.symbols import safe_ticker_component
+from tradingagents.decision_log import TradingMemoryLog
 from tradingagents.graph.trading_graph import TradingAgentsGraph
 
 logger = logging.getLogger(__name__)

tradingagents/graph/trading_graph.py

@@ -10,11 +10,11 @@ from typing import Any
 
 from tradingagents.agents.context import build_instrument_context, resolve_instrument_identity
 from tradingagents.agents.rating import parse_rating
-from tradingagents.agents.utils.memory import TradingMemoryLog
 from tradingagents.dataflows.config import run_config, set_config
 from tradingagents.dataflows.date_window import get_current_date
 from tradingagents.dataflows.symbols import safe_ticker_component
 from tradingagents.dataflows.vendors.yahoo.market import get_closes
+from tradingagents.decision_log import TradingMemoryLog
 from tradingagents.default_config import DEFAULT_CONFIG
 from tradingagents.llm_clients import create_llm_client
 from tradingagents.reporting import write_report_tree