Add HEDGE_PO_MODE instance modes with shared sim/live path.

Lock one mode per instance/subaccount, cross-asset BTC option/ETH perp sizing, combo-U exit, and ship docs/tests/audit.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/env/env_schema.py

@@ -109,6 +109,8 @@ HOT_RELOAD_EXACT = frozenset({
     "MAX_ACTIVE_HEDGE_PLANS",
     "HEDGE_PLAN_LIVE_ORDER",
     "HEDGE_PLAN_OPTION_PRIMARY",
+    "HEDGE_PO_MODE",
+    "HEDGE_CROSS_NOTIONAL_K",
     "HEDGE_PLAN_OPEN_ORDER",
     "HEDGE_PLAN_ON_PERP_SL_CLOSE_OPTIONS",
     "HEDGE_PLAN_ON_PERP_TP_CLOSE_OPTIONS",
@@ -177,6 +179,11 @@ SELECT_OPTIONS: dict[str, tuple[tuple[str, str], ...]] = {
         ("true", "以期权为主"),
         ("false", "保险模式"),
     ),
+    "HEDGE_PO_MODE": (
+        ("eth", "ETH永期(期权+永续同ETH)"),
+        ("btc", "BTC永期(期权+永续同BTC)"),
+        ("btc_eth", "跨币(BTC期权+ETH永续)"),
+    ),
     "SIM_DEFAULT_MODE": (
         ("sim", "模拟盘"),
         ("live", "实盘"),