feat(mcp-deribit,mcp-bybit): add place_combo_order

Deribit: private/create_combo + place_order sul combo instrument → una
sola crociata di spread invece di N (slippage atteso ridotto su
strutture liquide). ACL core + leverage cap su tutti i leg.

Bybit: place_batch_order su category=option (atomic multi-leg, 1
round-trip API). Reject su category != option (perp/linear non
supportano batch nativo). orderLinkId auto-generato per leg.

Tutti i test: deribit 48/48, bybit 123/123.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/mcp-deribit/src/mcp_deribit/client.py

@@ -1401,6 +1401,38 @@ class DeribitClient:
             return {"error": raw.get("error", "unknown"), "state": "error"}
         return r
 
+    async def place_combo_order(
+        self,
+        legs: list[dict[str, Any]],
+        side: str,
+        amount: float,
+        type: str = "limit",
+        price: float | None = None,
+        label: str | None = None,
+    ) -> dict:
+        """Crea un combo via private/create_combo poi piazza un singolo ordine
+        (buy/sell) sull'instrument_name del combo. Una sola crociata di spread
+        invece di N (uno per leg) → minor slippage su strutture liquide.
+
+        legs: [{instrument_name, direction: 'buy'|'sell', ratio: int}].
+        """
+        combo_raw = await self._request("private/create_combo", {"trades": legs})
+        combo = combo_raw.get("result")
+        if combo is None:
+            return {"state": "error", "error": combo_raw.get("error", "unknown")}
+        combo_instrument = combo.get("instrument_name") or combo.get("id")
+        order = await self.place_order(
+            instrument_name=combo_instrument,
+            side=side,
+            amount=amount,
+            type=type,
+            price=price,
+            label=label,
+        )
+        if order.get("state") == "error":
+            return {"state": "error", "error": order.get("error"), "combo_instrument": combo_instrument}
+        return {"combo_instrument": combo_instrument, **order}
+
     async def set_leverage(self, instrument_name: str, leverage: int) -> dict:
         """CER-016: pre-set account leverage per evitare default 50x testnet."""
         raw = await self._request(