malkhut(wire): OrderType as three orthogonal dimensions — Fable's corrections

CRITICAL REFACTOR based on Fable's review (S9 roadmap item):

Before: flat enum conflating order types with TIF/instructions
  OrderType had MARKET, LIMIT, IOC, FOK, POST_ONLY, REDUCE_ONLY, etc.

After: three orthogonal dimensions (FIX-aligned):
  1. OrderType (Tag 40): what the order IS
     LIMIT, MARKET, STOP_MARKET, STOP_LIMIT, TRIGGER_MARKET, TRIGGER_LIMIT,
     TRAILING_STOP, OCO, TP_SL
  2. TimeInForce (Tag 59): how long it LIVES
     GTC, IOC, FOK, GTD
  3. Instructions (Tag 18): behavioral modifiers
     POST_ONLY, REDUCE_ONLY, HIDDEN, ICEBERG

Key corrections:
- POST_ONLY is an instruction on a LIMIT order, not a standalone type
- IOC/FOK are TimeInForce values, not order types
- BingX trailing_stop -> native TRAILING_STOP_MARKET (not TRIGGER_MARKET)
- FulfilmentAction.time_in_force: new field, default GTC

Exchange mappings restructured:
  EXCHANGE_ORDER_TYPE_MAP: OrderType -> exchange native 'type' param
  EXCHANGE_TIF_MAP: TimeInForce -> exchange native 'timeInForce' param
  EXCHANGE_INSTRUCTION_MAP: Instruction -> exchange encoding

21 files changed. 380+ tests pass. Backward compatible.

MALKHUT/malkhut/tests/test_cwm.py

@@ -103,7 +103,7 @@ class TestExchangeMechanics:
         cwm = MinimalCryptoLOBCWM()
         state = _default_state()
         action = FulfilmentAction(
-            ActionKind.PLACE, Side.BUY, OrderType.POST_ONLY, 0, 0.10, 200,
+            ActionKind.PLACE, Side.BUY, OrderType.LIMIT, 0, 0.10, 200,
             post_only=True,
         )
         result = cwm.transition(state, (action,))
@@ -113,7 +113,7 @@ class TestExchangeMechanics:
         from malkhut.state import OpenOrderState
         oo = OpenOrderState(
             client_order_id="test_123", venue_order_id="v_123",
-            symbol="BTCUSDT", side=Side.BUY, order_type=OrderType.POST_ONLY,
+            symbol="BTCUSDT", side=Side.BUY, order_type=OrderType.LIMIT,
             price=50000.0, qty=0.001, remaining_qty=0.001,
             queue_ahead_estimate=0.001, created_ts_ns=1_000_000_000,
             last_update_ts_ns=1_000_000_000, post_only=True,
@@ -136,7 +136,7 @@ class TestExchangeMechanics:
         state = _default_state()
         # Post-only buy at best_ask should be rejected
         action = FulfilmentAction(
-            ActionKind.PLACE, Side.BUY, OrderType.POST_ONLY, -1, 0.10, 200,
+            ActionKind.PLACE, Side.BUY, OrderType.LIMIT, -1, 0.10, 200,
             post_only=True,
         )
         result = cwm.transition(state, (action,))
@@ -148,7 +148,7 @@ class TestPriceMaterialization:
     def test_cross_spread_buy_returns_best_ask(self):
         state = _default_state()
         action = FulfilmentAction(
-            ActionKind.CROSS_SPREAD, Side.BUY, OrderType.IOC, 0, 0.10, 50,
+            ActionKind.CROSS_SPREAD, Side.BUY, OrderType.LIMIT, 0, 0.10, 50,
         )
         price = materialize_price_from_action(state, action)
         assert price == 50001.0
@@ -156,7 +156,7 @@ class TestPriceMaterialization:
     def test_cross_spread_sell_returns_best_bid(self):
         state = _default_state()
         action = FulfilmentAction(
-            ActionKind.CROSS_SPREAD, Side.SELL, OrderType.IOC, 0, 0.10, 50,
+            ActionKind.CROSS_SPREAD, Side.SELL, OrderType.LIMIT, 0, 0.10, 50,
         )
         price = materialize_price_from_action(state, action)
         assert price == 50000.0
@@ -164,7 +164,7 @@ class TestPriceMaterialization:
     def test_buy_offset_0_returns_best_bid(self):
         state = _default_state()
         action = FulfilmentAction(
-            ActionKind.PLACE, Side.BUY, OrderType.POST_ONLY, 0, 0.10, 200,
+            ActionKind.PLACE, Side.BUY, OrderType.LIMIT, 0, 0.10, 200,
         )
         price = materialize_price_from_action(state, action)
         assert price == 50000.0