fix(resolution): cast $3 explicitly in close_paper_position and persist before mutating portfolio

Cycle-10 resolution check found market 562186 resolved (Paxton YES) but the
close failed with asyncpg AmbiguousParameterError: Postgres cannot infer the
type of a bare '$3 IS NOT NULL' in the close_pnl CASE. Reproduced via PREPARE
in the postgres pod; fixed by casting every $3 use to double precision.

The failed DB write also left memory/DB diverged: close_position() popped the
position and credited cash before persisting, so the retry at cycle 20 skipped
the market (pnl=n/a) while the DB row stayed open. Now the DB write happens
first and memory mutates only on success; check_resolutions() also isolates
per-market close failures so one error doesn't abort the cycle.

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

tests/test_paper_close.py

@@ -103,3 +103,28 @@ def test_unknown_market_returns_none():
         ex = PaperExecutor(db=FakeDB({}), bankroll=1000.0)
         return await ex.close_position("nope", 1.0)
     assert asyncio.run(run()) is None
+
+
+def test_db_failure_keeps_position_for_retry():
+    """Regression: a DB error during close must not mutate the in-memory
+    portfolio — otherwise the next resolution check skips the market
+    (not in positions) and the DB row stays open forever."""
+
+    class FailingDB(FakeDB):
+        async def close_paper_position(self, market_id, reason="", resolution=None):
+            raise RuntimeError("db down")
+
+    async def run():
+        db = FailingDB({
+            "mkt1": [{"direction": "BUY_YES", "shares": 200.0, "net_cost": 102.0}],
+        })
+        ex = PaperExecutor(db=db, bankroll=1000.0)
+        ex._portfolio.cash = 898.0
+        ex._portfolio.positions["mkt1"] = 100.0
+        with pytest.raises(RuntimeError):
+            await ex.close_position("mkt1", 1.0)
+        return ex
+
+    ex = asyncio.run(run())
+    assert ex._portfolio.positions == {"mkt1": 100.0}   # still open in memory
+    assert ex._portfolio.cash == pytest.approx(898.0)   # payout not credited