feat(V2): unified /mcp interface; retire Bybit/Alpaca to old/

Add a common cross-exchange interface (/mcp) over the integrated venues
(deribit, hyperliquid):

- get_instruments: uniform schema where each row carries its own
  `exchange`, `fees` (maker/taker, live from Deribit, null where the
  venue has no per-instrument schedule) and `history_start` (listing
  date, live from Deribit creation_timestamp), plus type/tick_size and a
  lossless `native` blob. Optional `exchange` filter; fan-out otherwise.
- get_historical: generalized to {exchange, instrument, interval,
  start_date, end_date}, returning a single chosen venue's candles.
  Consensus merge stays available on /mcp-cross.

New: routers/unified.py, exchanges/cross/instruments.py (normalizers),
UnifiedClient in cross/client.py, schemas in cross/tools.py. Deribit
get_instruments now also surfaces maker/taker_commission and
creation_timestamp (additive).

Retire Bybit and Alpaca from the API surface: move clients, routers,
settings classes and their tests under old/ (history preserved via
git mv); drop them from the builder, /mcp-cross dispatch and symbol_map.
Bybit remains a public funding/OI data source in sentiment (not the
trading client). IBKR is intentionally excluded from /mcp for now.

Docs: rewrite API_REFERENCE.md (remove Bybit/Alpaca, document /mcp,
clarify that data_timestamp is injected globally by middleware).

Tests: add unified-interface coverage; update cross/settings/builder/boot
tests for the reduced venue set. Fix a pre-existing flaky assertion in
the Hyperliquid signing test (r/s use eth_utils.to_hex like the official
SDK, so a leading zero byte yields <66 chars ~1/256 of the time).

323 passed, ruff clean.

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

src/cerbero_mcp/exchanges/cross/tools.py

@@ -1,13 +1,14 @@
-"""Pydantic schemas + thin tool wrappers for the /mcp-cross router."""
+"""Pydantic schemas + thin tool wrappers for the /mcp-cross and /mcp routers."""
 from __future__ import annotations
 
 from typing import Literal
 
 from pydantic import BaseModel
 
-from cerbero_mcp.exchanges.cross.client import CrossClient
+from cerbero_mcp.exchanges.cross.client import CrossClient, UnifiedClient
 
-AssetClass = Literal["crypto", "stocks"]
+AssetClass = Literal["crypto"]
+Exchange = Literal["deribit", "hyperliquid"]
 
 
 class GetHistoricalReq(BaseModel):
@@ -26,3 +27,39 @@ async def get_historical(client: CrossClient, params: GetHistoricalReq) -> dict:
         start_date=params.start_date,
         end_date=params.end_date,
     )
+
+
+# ── Unified /mcp interface ────────────────────────────────────────────
+
+class GetInstrumentsReq(BaseModel):
+    exchange: Exchange | None = None  # None → fan-out over all integrated venues
+    currency: str = "BTC"             # Deribit only
+    kind: str | None = "future"       # Deribit only: future | option | spot
+
+
+class UnifiedGetHistoricalReq(BaseModel):
+    exchange: Exchange
+    instrument: str
+    interval: str = "1h"
+    start_date: str
+    end_date: str
+
+
+async def get_instruments(client: UnifiedClient, params: GetInstrumentsReq) -> dict:
+    return await client.get_instruments(
+        exchange=params.exchange,
+        currency=params.currency,
+        kind=params.kind,
+    )
+
+
+async def unified_get_historical(
+    client: UnifiedClient, params: UnifiedGetHistoricalReq
+) -> dict:
+    return await client.get_historical(
+        exchange=params.exchange,
+        instrument=params.instrument,
+        interval=params.interval,
+        start_date=params.start_date,
+        end_date=params.end_date,
+    )