fix: resolve async execution and position storage issues

- Fix async call in model_day_executor.py by wrapping with asyncio.run()
  Resolves RuntimeWarning where run_trading_session coroutine was never awaited
- Remove register_agent() call in API mode to prevent file-based position storage
  Position data is now stored exclusively in SQLite database (jobs.db)
- Update test mocks to use AsyncMock for async run_trading_session method

This fixes production deployment issues:
1. Trading sessions now execute properly (async bug)
2. No position files created, database-only storage
3. All tests pass

Closes issue with no trades being executed in production

api/model_day_executor.py

@@ -11,6 +11,7 @@ This module provides:
 
 import logging
 import os
+import asyncio
 from typing import Dict, Any, Optional, List, TYPE_CHECKING
 from pathlib import Path
 
@@ -118,7 +119,7 @@ class ModelDayExecutor:
 
             # Run trading session
             logger.info(f"Running trading session for {self.model_sig} on {self.date}")
-            session_result = agent.run_trading_session(self.date)
+            session_result = asyncio.run(agent.run_trading_session(self.date))
 
             # Persist results to SQLite
             self._write_results_to_db(agent, session_result)
@@ -211,8 +212,10 @@ class ModelDayExecutor:
             init_date=config.get("date_range", {}).get("init_date", "2025-10-13")
         )
 
-        # Register agent (creates initial position if needed)
-        agent.register_agent()
+        # Note: In API mode, we don't call register_agent() because:
+        # - Position data is stored in SQLite database, not files
+        # - Database initialization is handled by JobManager
+        # - File-based position tracking is only for standalone/CLI mode
 
         return agent