debug: add comprehensive logging for position tracking bug investigation

Add debug logging to diagnose negative cash position issue where trades
calculate from initial $10,000 instead of accumulating.

Issue: After 11 trades, final cash shows -$8,768.68. Each trade appears
to calculate from $10,000 starting position instead of previous trade's
ending position.

Hypothesis: ContextInjector._current_position not updating after trades,
possibly due to MCP result type mismatch in isinstance(result, dict) check.

Debug logging added:
- agent/context_injector.py: Log MCP result type, content, and whether
  _current_position updates after each trade
- agent_tools/tool_trade.py: Log whether injected position is used vs
  DB query, and full contents of returned position dict

This will help identify:
1. What type is returned by MCP tool (dict vs other)
2. Whether _current_position is None on subsequent trades
3. What keys are present in returned position dicts

Related to issue where reasoning summary claims no trades executed
despite 4 sell orders being recorded.

agent/context_injector.py

@@ -88,9 +88,18 @@ class ContextInjector:
 
         # Update position state after successful trade
         if request.name in ["buy", "sell"]:
+            # Debug: Log result type and structure
+            print(f"[DEBUG ContextInjector] Trade result type: {type(result)}")
+            print(f"[DEBUG ContextInjector] Trade result: {result}")
+            print(f"[DEBUG ContextInjector] isinstance(result, dict): {isinstance(result, dict)}")
+
             # Check if result is a valid position dict (not an error)
             if isinstance(result, dict) and "error" not in result and "CASH" in result:
                 # Update our tracked position with the new state
                 self._current_position = result.copy()
+                print(f"[DEBUG ContextInjector] Updated _current_position: {self._current_position}")
+            else:
+                print(f"[DEBUG ContextInjector] Did NOT update _current_position - check failed")
+                print(f"[DEBUG ContextInjector] _current_position remains: {self._current_position}")
 
         return result

agent_tools/tool_trade.py

@@ -132,11 +132,14 @@ def _buy_impl(symbol: str, amount: int, signature: str = None, today_date: str =
         # Step 1: Get current position
         # Use injected position if available (for intra-day tracking),
         # otherwise query database for starting position
+        print(f"[DEBUG buy] _current_position received: {_current_position}")
         if _current_position is not None:
             current_position = _current_position
             next_action_id = 0  # Not used in new schema
+            print(f"[DEBUG buy] Using injected position: {current_position}")
         else:
             current_position, next_action_id = get_current_position_from_db(job_id, signature, today_date)
+            print(f"[DEBUG buy] Queried position from DB: {current_position}")
 
         # Step 2: Get stock price
         try:
@@ -189,6 +192,8 @@ def _buy_impl(symbol: str, amount: int, signature: str = None, today_date: str =
 
         conn.commit()
         print(f"[buy] {signature} bought {amount} shares of {symbol} at ${this_symbol_price}")
+        print(f"[DEBUG buy] Returning new_position: {new_position}")
+        print(f"[DEBUG buy] new_position keys: {list(new_position.keys())}")
         return new_position
 
     except Exception as e: