feat: migrate trade tools to write to actions table (new schema)

This commit implements Task 1 from the schema migration plan:
- Trade tools (buy/sell) now write to actions table instead of old positions table
- Added trading_day_id parameter to buy/sell functions
- Updated ContextInjector to inject trading_day_id
- Updated RuntimeConfigManager to include TRADING_DAY_ID in config
- Removed P&L calculation from trade functions (now done at trading_days level)
- Added tests verifying correct behavior with new schema

Changes:
- agent_tools/tool_trade.py: Modified _buy_impl and _sell_impl to write to actions table
- agent/context_injector.py: Added trading_day_id parameter and injection logic
- api/model_day_executor.py: Updated to read trading_day_id from runtime config
- api/runtime_manager.py: Added trading_day_id to config initialization
- tests/unit/test_trade_tools_new_schema.py: New tests for new schema compliance

All tests passing.

api/model_day_executor.py

@@ -138,11 +138,15 @@ class ModelDayExecutor:
 
             # Create and inject context with correct values
             from agent.context_injector import ContextInjector
+            from tools.general_tools import get_config_value
+            trading_day_id = get_config_value('TRADING_DAY_ID')  # Get from runtime config
+
             context_injector = ContextInjector(
                 signature=self.model_sig,
                 today_date=self.date,  # Current trading day
                 job_id=self.job_id,
-                session_id=session_id
+                session_id=session_id,
+                trading_day_id=trading_day_id
             )
             logger.info(f"[DEBUG] ModelDayExecutor: Created ContextInjector with signature={self.model_sig}, date={self.date}, job_id={self.job_id}, session_id={session_id}")
             logger.info(f"[DEBUG] ModelDayExecutor: Calling await agent.set_context()")