feat(resolution): add automatic market resolution detector with conservative payout validation

- PolymarketClient.get_market_resolution(): query Gamma API by market id;
  resolved only when closed AND uma status final AND outcome prices binary
  (never settle on disputed/ambiguous outcomes)
- bot/main.py: check_resolutions() runs every 10 cycles (~10 min) in paper
  mode, settles open positions via PaperExecutor.close_position()
- close_reason now persisted as 'resolved' (resolution has its own column)
- tests/test_resolution_detector.py: 10 tests covering API parsing shapes
  and the BUY_NO settlement flow; 27/27 suite green

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

bot/data/polymarket.py

@@ -211,6 +211,32 @@ class Market:
     category: str = ""
 
 
+@dataclass
+class MarketResolution:
+    """Resolution state of a market, from Gamma API.
+
+    resolution is the final YES outcome price: 1.0 = YES won, 0.0 = NO won.
+    resolved is True only when the outcome is definitive — a market that is
+    closed but still in UMA dispute/proposal reports resolved=False.
+    """
+    resolved: bool
+    resolution: Optional[float] = None
+    resolved_at: Optional[datetime] = None
+
+
+def _parse_resolution_timestamp(raw: Optional[str]) -> Optional[datetime]:
+    """Parse Gamma timestamps: '2026-06-11 13:15:01+00' or '2026-06-11T13:15:01Z'."""
+    if not raw:
+        return None
+    try:
+        dt = datetime.fromisoformat(raw.replace("Z", "+00:00"))
+        if dt.tzinfo is None:
+            dt = dt.replace(tzinfo=timezone.utc)
+        return dt
+    except (ValueError, TypeError):
+        return None
+
+
 @dataclass
 class OrderBook:
     market_id: str
@@ -447,6 +473,74 @@ class PolymarketClient:
         )
         return markets
 
+    async def get_market_resolution(self, market_id: str) -> Optional[MarketResolution]:
+        """Fetch resolution state for a market by Gamma market id.
+
+        Observed Gamma API behaviour (GET /markets/{id}):
+          open market     → closed=false, umaResolutionStatus absent
+          resolved market → closed=true, umaResolutionStatus="resolved",
+                            outcomePrices='["0", "1"]' (final YES price = outcome)
+          unknown id      → HTTP 404
+
+        Returns None on API errors (caller retries next check). A closed market
+        whose outcome prices are not degenerate (0/1) or whose UMA status is not
+        "resolved" yet (proposed/disputed) reports resolved=False — we never
+        settle a position on an ambiguous outcome.
+        """
+        try:
+            resp = await self._client.get(f"{GAMMA_API}/markets/{market_id}")
+            if resp.status_code == 404:
+                log.warning("get_market_resolution: market %s not found (404)", market_id)
+                return None
+            resp.raise_for_status()
+            m = resp.json()
+        except httpx.HTTPError as e:
+            log.warning("get_market_resolution: API error for %s: %s", market_id, e)
+            return None
+
+        if not m.get("closed"):
+            return MarketResolution(resolved=False)
+
+        uma_status = (m.get("umaResolutionStatus") or "").lower()
+        if uma_status and uma_status != "resolved":
+            # Closed but UMA outcome still proposed/disputed — wait for finality
+            return MarketResolution(resolved=False)
+
+        raw_prices = m.get("outcomePrices", [])
+        if isinstance(raw_prices, str):
+            import json as _json
+            try:
+                raw_prices = _json.loads(raw_prices)
+            except ValueError:
+                raw_prices = []
+        try:
+            yes_final = float(raw_prices[0])
+        except (IndexError, TypeError, ValueError):
+            log.warning(
+                "get_market_resolution: market %s closed but outcomePrices "
+                "unparseable: %r", market_id, m.get("outcomePrices"),
+            )
+            return MarketResolution(resolved=False)
+
+        if yes_final >= 0.99:
+            resolution = 1.0
+        elif yes_final <= 0.01:
+            resolution = 0.0
+        else:
+            # Closed but prices not settled at 0/1 (partial / ambiguous outcome)
+            log.warning(
+                "get_market_resolution: market %s closed with non-binary final "
+                "price %.3f — not settling", market_id, yes_final,
+            )
+            return MarketResolution(resolved=False)
+
+        resolved_at = (
+            _parse_resolution_timestamp(m.get("closedTime"))
+            or _parse_resolution_timestamp(m.get("umaEndDate"))
+            or _parse_resolution_timestamp(m.get("endDate"))
+        )
+        return MarketResolution(resolved=True, resolution=resolution, resolved_at=resolved_at)
+
     async def get_order_book(self, token_id: str) -> Optional[OrderBook]:
         """Get order book for a specific token."""
         try: