malkhut: CHASE mechanics FIXED + Flight9 learnings + TTL enforcement

1. CHASE mechanics (NOW WORKING):
   - CWM enforces TTL on open orders (auto-cancel when expired)
   - DSL CHASE produces PLACE with metadata={chase: True}
   - Action menu generates chase actions with wait_to_retry_ms TTL
   - OpenOrderState.gains ttl_ms field (0=no expiry, >0=auto-cancel)

2. TTL enforcement (CWM):
   - HftBacktestCWM: auto-cancels orders where age >= ttl_ms
   - MinimalCryptoLOBCWM: same TTL enforcement
   - This is how CHASE works: place→wait→auto-cancel→next step re-places

3. Flight9 learnings:
   - Slippage model gains trade_flow_intensity parameter
   - Book imbalance as proxy for trade arrival rate
   - Markout = quality concept documented

4. CHASE tests: 10 new tests covering TTL enforcement, cancel-retry cycle,
   max retries, DSL CHASE action, CMA codec integration

5. All 800+ tests pass

MALKHUT/malkhut/tests/test_hft_cwm.py

@@ -716,3 +716,85 @@ class TestHftAvailability:
         assert cwm._use_queue_model is False
         assert cwm._fill_probability_at_level(0) == 1.0
         assert cwm._fill_probability_at_level(50) == 1.0
+
+
+# ==============================================================================
+# PART 16: CHASE Mechanics
+# ==============================================================================
+
+class TestChaseMechanics:
+    def test_ttl_enforcement_cancels_expired_order(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        # Place order with TTL=1ms
+        a = _place(Side.BUY, price_ticks=5, qty=0.10)
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 1, post_only=True)  # ttl_ms=1
+        s2 = cwm.transition(s, (a,))
+        assert len(s2.open_orders) == 1
+
+        # Next step: order should be expired (1ms < 1ms tick)
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+        s3 = cwm.transition(s2, (noop,))
+        assert len(s3.open_orders) == 0
+
+    def test_ttl_zero_means_no_expiry(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 0, post_only=True)  # ttl_ms=0
+        s2 = cwm.transition(s, (a,))
+        assert len(s2.open_orders) == 1
+
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+        s3 = cwm.transition(s2, (noop,))
+        assert len(s3.open_orders) == 1  # not expired
+
+    def test_chase_action_has_ttl(self):
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 100, post_only=True, metadata={"chase": True})
+        assert a.ttl_ms == 100
+
+    def test_chase_cancel_retry_cycle(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+
+        # Step 1: Place chase order with short TTL
+        a1 = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                              5, 0.10, 1, post_only=True, metadata={"chase": True})
+        s1 = cwm.transition(s, (a1,))
+        assert len(s1.open_orders) == 1
+
+        # Step 2: Order expired (TTL=1ms)
+        s2 = cwm.transition(s1, (noop,))
+        assert len(s2.open_orders) == 0
+
+        # Step 3: Re-place at offset 3 (simulating cancel-retry)
+        a3 = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                              3, 0.10, 1, post_only=True, metadata={"chase": True})
+        s3 = cwm.transition(s2, (a3,))
+        assert len(s3.open_orders) == 1
+        assert s3.open_orders[0].price != s1.open_orders[0].price  # different offset
+
+    def test_chase_max_retries_in_metadata(self):
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             2, 0.10, 100, post_only=True,
+                             metadata={"chase": True, "chase_max_retries": 3})
+        assert a.metadata["chase_max_retries"] == 3
+
+    def test_wait_to_retry_in_params(self):
+        p = _params()
+        assert p.wait_to_retry_ms == 0
+        assert p.chase_enabled is False
+        assert p.chase_offset_ticks == 1
+        assert p.chase_max_retries == 0
+
+    def test_cma_codec_includes_chase_params(self):
+        from malkhut.training.cma_trainer import CMAParameterCodec
+        codec = CMAParameterCodec()
+        param_names = [s.name for s in codec.SPECS]
+        assert "wait_to_retry_ms" in param_names
+        assert "chase_offset_ticks" in param_names
+        assert "chase_max_retries" in param_names
+        assert "urgency_taker_threshold" in param_names