feat: replace per-agent BM25 memory with persistent append-only decision log

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tradingagents/agents/__init__.py

@@ -1,6 +1,5 @@
 from .utils.agent_utils import create_msg_delete
 from .utils.agent_states import AgentState, InvestDebateState, RiskDebateState
-from .utils.memory import FinancialSituationMemory
 
 from .analysts.fundamentals_analyst import create_fundamentals_analyst
 from .analysts.market_analyst import create_market_analyst
@@ -20,7 +19,6 @@ from .managers.portfolio_manager import create_portfolio_manager
 from .trader.trader import create_trader
 
 __all__ = [
-    "FinancialSituationMemory",
     "AgentState",
     "create_msg_delete",
     "InvestDebateState",