refactor: remove block-sequential gate path and gate_block knob (algo #6)

config/train_videomme.yaml 同时收录待入库的实验配置变更(run_id v2 /
concurrency 32 / batch_size 40)。tests/integration/test_v3_contract_e2e.py
的 run_id 断言按 Task 5 显式契约同步修正(原断言依赖旧隐式实例注入)。

tests/unit/test_harness_config.py

@@ -50,7 +50,6 @@ def _valid_kwargs() -> dict:
         "gate_delta_min": 0.02,
         "gate_lambda_dir": -0.642,
         "gate_e_rollback": 10.0,
-        "gate_block": 8,
         "gate_n_max": 40,
         "gate_p_low": 0.05,
         "gate_p_high": 0.95,
@@ -378,16 +377,16 @@ class TestGateValidation:
         with pytest.raises(ValueError, match="gate_lambda_dir"):
             _validate(cfg)
 
-    def test_block_exceeds_n_max_rejected(self) -> None:
-        """gate_block > gate_n_max 应抛出 ValueError。"""
-        cfg = _make_config(gate_block=50, gate_n_max=40)
-        with pytest.raises(ValueError, match="gate_block"):
+    def test_n_max_zero_rejected(self) -> None:
+        """gate_n_max <= 0 应抛出 ValueError（迁移自块序贯版 gate_block 校验）。"""
+        cfg = _make_config(gate_n_max=0)
+        with pytest.raises(ValueError, match="gate_n_max"):
             _validate(cfg)
 
-    def test_block_zero_rejected(self) -> None:
-        """gate_block <= 0 应抛出 ValueError。"""
-        cfg = _make_config(gate_block=0)
-        with pytest.raises(ValueError, match="gate_block"):
+    def test_n_max_negative_rejected(self) -> None:
+        """gate_n_max 为负也应报错。"""
+        cfg = _make_config(gate_n_max=-1)
+        with pytest.raises(ValueError, match="gate_n_max"):
             _validate(cfg)
 
     def test_p_low_exceeds_p_high_rejected(self) -> None: