feat(kevin): correct exits, realized P&L, wire exit scanner

- executor: EXIT/SELL signals close the FULL held broker position (not a target_dollars-sized fresh order) and skip when flat

- executor: book realized P&L on the closing trade ((fill - avg_entry)*qty) so the dashboard P&L + win-rate populate; entries leave pnl=None

- exit scanner: wired into the bridge run loop on kevin_bridge_exit_scan_cron (daily ET gate; croniter intentionally not a dependency) plus an offsetting-SELL guard so it only emits exits for currently-held tickers

[ci skip]

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/services/kevin_signal_bridge/test_exit_scanner.py

@@ -7,8 +7,6 @@ from unittest.mock import AsyncMock, MagicMock
 import pytest
 from sqlalchemy.ext.asyncio import AsyncSession
 
-pytestmark = pytest.mark.integration
-
 from services.kevin_signal_bridge.exit_scanner import ExitScanner
 from shared.constants.kevin import KEVIN_STRATEGY_UUID
 from shared.models.meet_kevin import (
@@ -23,6 +21,9 @@ from shared.models.meet_kevin import (
 )
 from shared.models.meet_kevin_trading import BridgeStatus, KevinSignalBridgeState
 from shared.models.trading import Trade, TradeSide, TradeStatus
+from shared.schemas.trading import PositionInfo
+
+pytestmark = pytest.mark.integration
 
 
 def _factory(session: AsyncSession):
@@ -39,6 +40,25 @@ def _factory(session: AsyncSession):
     return factory
 
 
+def _broker_holding(*tickers: str):
+    """Mock broker reporting the given tickers as currently held."""
+    broker = AsyncMock()
+    broker.get_positions = AsyncMock(
+        return_value=[
+            PositionInfo(
+                ticker=t,
+                qty=10.0,
+                avg_entry=100.0,
+                current_price=110.0,
+                unrealized_pnl=100.0,
+                market_value=1100.0,
+            )
+            for t in tickers
+        ]
+    )
+    return broker
+
+
 async def _seed_video_and_mention(session: AsyncSession) -> int:
     channel = KevinChannel(youtube_channel_id="UCex", title="t")
     session.add(channel)
@@ -111,7 +131,10 @@ async def test_exit_scanner_emits_on_elapsed_hold(db_session: AsyncSession):
     config = MagicMock(kevin_hold_days={"unspecified": 10})
 
     scanner = ExitScanner(
-        session_factory=_factory(db_session), publisher=publisher, config=config
+        session_factory=_factory(db_session),
+        publisher=publisher,
+        config=config,
+        broker=_broker_holding("NVDA"),
     )
     emitted = await scanner.scan_and_emit_exits()
     assert emitted == 1
@@ -149,7 +172,10 @@ async def test_exit_scanner_does_not_emit_when_hold_not_elapsed(
     config = MagicMock(kevin_hold_days={"unspecified": 10})
 
     scanner = ExitScanner(
-        session_factory=_factory(db_session), publisher=publisher, config=config
+        session_factory=_factory(db_session),
+        publisher=publisher,
+        config=config,
+        broker=_broker_holding("NVDA"),
     )
     emitted = await scanner.scan_and_emit_exits()
     assert emitted == 0