refactor(V2): get_instruments common-only on /mcp (enriched with Deribit filters)

Move get_instruments off the per-exchange Deribit router and onto the
unified interface, without losing the advanced Deribit filtering.

- /mcp/tools/get_instruments now accepts the Deribit-specific filters
  (currency, kind, expiry_from/to, strike_min/max, min_open_interest) and
  pagination (offset/limit). Venues that list everything (Hyperliquid)
  ignore them. Response adds `meta: {deribit: {total, offset, limit,
  has_more}}` surfacing per-source pagination.
- Remove /mcp-deribit/tools/get_instruments (endpoint + tool wrapper +
  GetInstrumentsReq schema). The DeribitClient.get_instruments METHOD
  stays — it's what the unified normalizer calls.

Tests: cover the enriched filters + meta passthrough; app-boot asserts
/mcp-deribit/tools/get_instruments is gone. Docs (API_REFERENCE/README/
CLAUDE) and smoke updated; also fixed the stale Hyperliquid tool count
(14 → 15) found during the doc check.

325 passed, ruff clean. Verified live: kind=option limit=5 → 5/940
has_more=true; /mcp-deribit/tools/get_instruments → 404.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/exchanges/cross/test_unified.py

@@ -68,11 +68,18 @@ class _FakeDeribit:
         self._raises = raises
 
     async def get_instruments(self, **kwargs: Any) -> dict[str, Any]:
-        return {"instruments": [{
-            "name": "BTC-PERPETUAL", "kind": "future", "tick_size": 0.5,
-            "maker_commission": 0.0, "taker_commission": 0.0005,
-            "creation_timestamp": 1534377600000,
-        }]}
+        self.inst_call = kwargs
+        return {
+            "instruments": [{
+                "name": "BTC-PERPETUAL", "kind": "future", "tick_size": 0.5,
+                "maker_commission": 0.0, "taker_commission": 0.0005,
+                "creation_timestamp": 1534377600000,
+            }],
+            "total": 1,
+            "offset": kwargs.get("offset", 0),
+            "limit": kwargs.get("limit", 100),
+            "has_more": False,
+        }
 
     async def get_historical(self, **kwargs: Any) -> dict[str, Any]:
         if self._raises:
@@ -136,6 +143,27 @@ async def test_get_instruments_unsupported_exchange_raises_400():
     assert exc.value.status_code == 400
 
 
+@pytest.mark.asyncio
+async def test_get_instruments_deribit_filters_and_meta():
+    fake = _FakeDeribit()
+    uc = UnifiedClient(_FakeRegistry({"deribit": fake}), env="mainnet")
+    out = await uc.get_instruments(
+        exchange="deribit", currency="ETH", kind="option",
+        strike_min=1000.0, expiry_to="2026-12-31", min_open_interest=5.0,
+        offset=5, limit=10,
+    )
+    # advanced Deribit filters reach the client
+    assert fake.inst_call["currency"] == "ETH"
+    assert fake.inst_call["kind"] == "option"
+    assert fake.inst_call["strike_min"] == 1000.0
+    assert fake.inst_call["expiry_to"] == "2026-12-31"
+    assert fake.inst_call["min_open_interest"] == 5.0
+    assert fake.inst_call["offset"] == 5 and fake.inst_call["limit"] == 10
+    # pagination metadata surfaced per source
+    assert out["meta"]["deribit"]["limit"] == 10
+    assert out["meta"]["deribit"]["has_more"] is False
+
+
 @pytest.mark.asyncio
 async def test_get_instruments_partial_failure_reports_failed():
     uc = UnifiedClient(_FakeRegistry({"deribit": _FakeDeribit()}), env="mainnet")