fix(critical): remove dead manifold.get_probability() from legacy scan and fix BUY_NO payout calculation

- Legacy scan called ManifoldClient.get_probability(), removed in the v3
  matcher migration, causing AttributeError when positions had changed
  family keys. The block used Manifold to escalate positions to
  CLOSE_RECOMMENDED (inversion detection) — a trading decision forbidden
  under MANIFOLD_SIGNAL_ENABLED=false — so the dependency is removed
  entirely; the scan keeps family re-keying and sibling-conflict logic.

- PaperExecutor.close_position() computed cash += position_cost * resolution,
  ignoring direction: a winning BUY_NO (resolution=0.0) paid out $0 and
  reported a loss. Now settles per trade:
    BUY_YES: payout = shares * resolution
    BUY_NO:  payout = shares * (1 - resolution)
  with pnl = payout - net_cost; Telegram win/loss keys off pnl > 0.
  Adds read-only Database.get_open_trades_for_market().

- tests/test_paper_close.py covers the 4 deterministic payout cases;
  tests/conftest.py shims datetime.UTC for local Python 3.10 (prod is 3.11).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_paper_close.py

@@ -0,0 +1,105 @@
+"""
+Tests for PaperExecutor.close_position() settlement payout.
+
+Regression: the old code computed cash += position_cost * resolution, which
+ignores direction — a winning BUY_NO (resolution = 0.0) paid out $0.
+
+Correct settlement:
+  BUY_YES: payout = shares * resolution
+  BUY_NO:  payout = shares * (1 - resolution)
+  pnl = payout - net_cost
+"""
+import asyncio
+
+import pytest
+
+from bot.executor import paper
+from bot.executor.paper import PaperExecutor
+
+
+class FakeDB:
+    """Minimal Database stub for close_position()."""
+
+    def __init__(self, trades_by_market: dict[str, list[dict]]):
+        self._trades = trades_by_market
+        self.closed: list[tuple] = []
+
+    async def get_open_trades_for_market(self, market_id: str) -> list[dict]:
+        return self._trades.get(market_id, [])
+
+    async def close_paper_position(self, market_id, reason="", resolution=None):
+        self.closed.append((market_id, reason, resolution))
+
+
+def _close(direction: str, resolution: float):
+    """Open one paper trade (size $100 @ 0.5 → 200 shares, net_cost $102)
+    and settle it at `resolution`. Returns (pnl, executor, notifications)."""
+    notifications: list[tuple] = []
+
+    async def fake_trade_closed(question, pnl):
+        notifications.append((question, pnl))
+
+    async def run():
+        db = FakeDB({
+            "mkt1": [{"direction": direction, "shares": 200.0, "net_cost": 102.0}],
+        })
+        ex = PaperExecutor(db=db, bankroll=1000.0)
+        ex._portfolio.cash = 898.0           # 1000 - net_cost spent at entry
+        ex._portfolio.positions["mkt1"] = 100.0  # size_usdc, as execute() stores it
+
+        original = paper.telegram.trade_closed
+        paper.telegram.trade_closed = fake_trade_closed
+        try:
+            pnl = await ex.close_position("mkt1", resolution, question="Test market?")
+            await asyncio.sleep(0)  # let the notification task run
+        finally:
+            paper.telegram.trade_closed = original
+        return pnl, ex, db
+
+    pnl, ex, db = asyncio.run(run())
+    return pnl, ex, db, notifications
+
+
+def test_buy_yes_wins():
+    pnl, ex, db, notif = _close("BUY_YES", resolution=1.0)
+    assert pnl == pytest.approx(200.0 - 102.0)   # payout = 200 * 1.0
+    assert pnl > 0
+    assert ex._portfolio.cash == pytest.approx(898.0 + 200.0)
+    assert notif[0][1] > 0                        # Telegram reports a win
+
+
+def test_buy_yes_loses():
+    pnl, ex, db, notif = _close("BUY_YES", resolution=0.0)
+    assert pnl == pytest.approx(-102.0)           # payout = 0
+    assert pnl < 0
+    assert ex._portfolio.cash == pytest.approx(898.0)
+    assert notif[0][1] < 0                        # Telegram reports a loss
+
+
+def test_buy_no_wins():
+    pnl, ex, db, notif = _close("BUY_NO", resolution=0.0)
+    assert pnl == pytest.approx(200.0 - 102.0)   # payout = 200 * (1 - 0.0)
+    assert pnl > 0
+    assert ex._portfolio.cash == pytest.approx(898.0 + 200.0)
+    assert notif[0][1] > 0                        # win despite resolution = 0.0
+
+
+def test_buy_no_loses():
+    pnl, ex, db, notif = _close("BUY_NO", resolution=1.0)
+    assert pnl == pytest.approx(-102.0)           # payout = 200 * (1 - 1.0) = 0
+    assert pnl < 0
+    assert ex._portfolio.cash == pytest.approx(898.0)
+    assert notif[0][1] < 0                        # loss despite resolution = 1.0
+
+
+def test_position_is_removed_and_persisted():
+    pnl, ex, db, notif = _close("BUY_YES", resolution=1.0)
+    assert "mkt1" not in ex._portfolio.positions
+    assert db.closed == [("mkt1", "market_resolved resolution=1.0", 1.0)]
+
+
+def test_unknown_market_returns_none():
+    async def run():
+        ex = PaperExecutor(db=FakeDB({}), bankroll=1000.0)
+        return await ex.close_position("nope", 1.0)
+    assert asyncio.run(run()) is None