fix(harness): Codex functional review 修复 — 命名/集成测试/delta_min/promote 消息

- _apply_env_overrides → _apply_env_var_overrides，docstring 明确从 os.environ 读取
- 新增 TestLoadConfigRealYaml：用真实 config/default.yaml 验证嵌套 harness 解析
- 新增 test_delta_min_negative_rejected：覆盖 gate_delta_min >= 0 校验
- 恢复 promote 模式独立错误消息（从合并分支分离回 TRM4 原始提示）
- 77 个单元测试全部通过，radon 全部 Grade B 或更好

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/test_harness_config.py

@@ -169,7 +169,7 @@ class TestModeValidation:
     def test_promote_requires_run_id_and_version(self) -> None:
         """promote 模式需同时提供 run_id 和 version。"""
         cfg = _make_config(mode="promote", run_id="", version="v1")
-        with pytest.raises(ValueError, match="run.id"):
+        with pytest.raises(ValueError, match="promote.*run-id"):
             _validate(cfg)
 
     def test_train_mode_requires_run_id_without_resume_fresh(self) -> None:
@@ -359,6 +359,12 @@ class TestGateValidation:
         with pytest.raises(ValueError, match="gate_w_net_min"):
             _validate(cfg)
 
+    def test_delta_min_negative_rejected(self) -> None:
+        """gate_delta_min < 0 应抛出 ValueError。"""
+        cfg = _make_config(gate_delta_min=-0.1)
+        with pytest.raises(ValueError, match="gate_delta_min"):
+            _validate(cfg)
+
     def test_lambda_dir_positive_rejected(self) -> None:
         """gate_lambda_dir >= 0 应抛出 ValueError。"""
         cfg = _make_config(gate_lambda_dir=0.5)
@@ -527,6 +533,34 @@ class TestLoadConfigEnvOverrides:
         assert cfg.workspace_dir == Path("/cli/workspace")
 
 
+# ──────────────────── test_load_config_real_yaml ─────────────────────────
+
+
+class TestLoadConfigRealYaml:
+    """用真实 config/default.yaml 验证 load_config 嵌套解析。"""
+
+    def test_load_config_real_default_yaml(self) -> None:
+        """真实 config/default.yaml 的 harness 段应正确解析并通过校验。"""
+        cfg = load_config(Path("config/default.yaml"), {})
+        assert cfg.mode == "infer"
+        assert cfg.gate_e_confirm == 20.0
+        assert cfg.batch_size == 15
+        assert cfg.concurrency == 12
+        assert cfg.workspace_dir == Path("workspaces/default")
+        assert cfg.store_dir == Path("store")
+        assert cfg.skill_mode == "auto"
+
+    def test_real_yaml_cli_override(self) -> None:
+        """真实 YAML + CLI 覆盖应正确合并。"""
+        cfg = load_config(
+            Path("config/default.yaml"),
+            {"concurrency": 4, "max_steps": 30},
+        )
+        assert cfg.concurrency == 4
+        assert cfg.max_steps == 30
+        assert cfg.mode == "infer"  # 未覆盖字段保持 YAML 值
+
+
 # ─────────────────────────── test_val_size_floor ─────────────────────────