fix: correct profit calculation to compare against start-of-day value

Previously, profit calculations compared portfolio value to the previous
day's final value. This caused trades to appear as losses since buying
stocks decreases cash and increases stock value equally (net zero change).

Now profit calculations compare to the start-of-day portfolio value
(action_id=0 for current date), which accurately reflects gains/losses
from price movements and trading decisions.

Changes:
- agent_tools/tool_trade.py: Fixed profit calc in _buy_impl() and _sell_impl()
- tools/price_tools.py: Fixed profit calc in add_no_trade_record_to_db()

Test: test_profit_calculation_accuracy now passes

agent_tools/tool_trade.py

@@ -141,20 +141,25 @@ def _buy_impl(symbol: str, amount: int, signature: str = None, today_date: str =
                 except KeyError:
                     pass  # Symbol price not available, skip
 
-        # Get previous portfolio value for P&L calculation
+        # Get start-of-day portfolio value (action_id=0 for today) for P&L calculation
         cursor.execute("""
             SELECT portfolio_value
             FROM positions
-            WHERE job_id = ? AND model = ? AND date < ?
-            ORDER BY date DESC, action_id DESC
+            WHERE job_id = ? AND model = ? AND date = ? AND action_id = 0
             LIMIT 1
         """, (job_id, signature, today_date))
 
         row = cursor.fetchone()
-        previous_value = row[0] if row else 10000.0  # Default initial value
 
-        daily_profit = portfolio_value - previous_value
-        daily_return_pct = (daily_profit / previous_value * 100) if previous_value > 0 else 0
+        if row:
+            # Compare to start of day (action_id=0)
+            start_of_day_value = row[0]
+            daily_profit = portfolio_value - start_of_day_value
+            daily_return_pct = (daily_profit / start_of_day_value * 100) if start_of_day_value > 0 else 0
+        else:
+            # First action of first day - no baseline yet
+            daily_profit = 0.0
+            daily_return_pct = 0.0
 
         # Step 6: Write to positions table
         created_at = datetime.utcnow().isoformat() + "Z"
@@ -284,20 +289,25 @@ def _sell_impl(symbol: str, amount: int, signature: str = None, today_date: str
                 except KeyError:
                     pass
 
-        # Get previous portfolio value
+        # Get start-of-day portfolio value (action_id=0 for today) for P&L calculation
         cursor.execute("""
             SELECT portfolio_value
             FROM positions
-            WHERE job_id = ? AND model = ? AND date < ?
-            ORDER BY date DESC, action_id DESC
+            WHERE job_id = ? AND model = ? AND date = ? AND action_id = 0
             LIMIT 1
         """, (job_id, signature, today_date))
 
         row = cursor.fetchone()
-        previous_value = row[0] if row else 10000.0
 
-        daily_profit = portfolio_value - previous_value
-        daily_return_pct = (daily_profit / previous_value * 100) if previous_value > 0 else 0
+        if row:
+            # Compare to start of day (action_id=0)
+            start_of_day_value = row[0]
+            daily_profit = portfolio_value - start_of_day_value
+            daily_return_pct = (daily_profit / start_of_day_value * 100) if start_of_day_value > 0 else 0
+        else:
+            # First action of first day - no baseline yet
+            daily_profit = 0.0
+            daily_return_pct = 0.0
 
         # Step 6: Write to positions table
         created_at = datetime.utcnow().isoformat() + "Z"

tools/price_tools.py

@@ -414,20 +414,25 @@ def add_no_trade_record_to_db(
                     logger.warning(f"Price not found for {symbol} on {today_date}")
                     pass
 
-        # Get previous value for P&L
+        # Get start-of-day portfolio value (action_id=0 for today) for P&L calculation
         cursor.execute("""
             SELECT portfolio_value
             FROM positions
-            WHERE job_id = ? AND model = ? AND date < ?
-            ORDER BY date DESC, action_id DESC
+            WHERE job_id = ? AND model = ? AND date = ? AND action_id = 0
             LIMIT 1
         """, (job_id, modelname, today_date))
 
         row = cursor.fetchone()
-        previous_value = row[0] if row else 10000.0
 
-        daily_profit = portfolio_value - previous_value
-        daily_return_pct = (daily_profit / previous_value * 100) if previous_value > 0 else 0
+        if row:
+            # Compare to start of day (action_id=0)
+            start_of_day_value = row[0]
+            daily_profit = portfolio_value - start_of_day_value
+            daily_return_pct = (daily_profit / start_of_day_value * 100) if start_of_day_value > 0 else 0
+        else:
+            # First action of first day - no baseline yet
+            daily_profit = 0.0
+            daily_return_pct = 0.0
 
         # Insert position record
         created_at = datetime.utcnow().isoformat() + "Z"