[moz] impl(§17): CI/部署失败 steps 分支指引 + 基础设施 Issue 转交流程

改动 1: ci_failure steps 增加分支指引（代码问题自己修/基础设施问题提Issue给姜维）
改动 2: deploy_failure steps 同上分支指引（2处定义都改）
改动 3: issue_assigned handler 按 type/infrastructure label 分流
  - infrastructure label → infrastructure_failure event_type（运维排查 steps）
  - 其他 → 原有编码 steps
改动 4: ToolchainApiSection 新增「需要创建 Issue 时」API 指引段落
改动 5: Red Flags 新增「不是我代码的问题」条目
测试: 8 个新测试，463 passed

tests/unit/test_toolchain_handler_v2.py

@@ -523,3 +523,73 @@ class TestFullPromptBuild:
         # Must have constraints with Red Flags
         assert "Red Flags" in prompt
         assert "强制要求" in prompt
+
+
+# ---------------------------------------------------------------------------
+# §17 v2: CI/deploy failure branching + issue label routing + Issue API guidance
+# ---------------------------------------------------------------------------
+
+class TestCiFailureBranching:
+    """ci_failure steps should include a/b branching guidance."""
+
+    def test_ci_failure_steps_contain_branching(self):
+        source_file = PROJECT_ROOT / "src" / "api" / "toolchain_routes.py"
+        source = source_file.read_text()
+        assert '基础设施问题' in source
+        assert 'type/infrastructure' in source
+        assert 'jiangwei-infra' in source
+
+
+class TestDeployFailureBranching:
+    """deploy_failure steps should include a/b branching guidance."""
+
+    def test_deploy_failure_steps_contain_branching(self):
+        source_file = PROJECT_ROOT / "src" / "api" / "toolchain_routes.py"
+        source = source_file.read_text()
+        count = source.count('基础设施问题（Gitea 不可用')
+        assert count >= 2, f'Expected >=2 deploy_failure branching, found {count}'
+
+
+class TestIssueAssignedLabelRouting:
+    """issue_assigned handler should route by type/infrastructure label."""
+
+    def test_label_check_in_source(self):
+        source_file = PROJECT_ROOT / "src" / "api" / "toolchain_routes.py"
+        source = source_file.read_text()
+        assert 'is_infrastructure' in source
+        assert 'infrastructure_failure' in source
+        assert '基础设施 Issue' in source
+
+    def test_normal_issue_keeps_coding_steps(self):
+        source_file = PROJECT_ROOT / "src" / "api" / "toolchain_routes.py"
+        source = source_file.read_text()
+        assert '创建分支 fix/' in source
+        assert 'issue_assigned' in source
+
+
+class TestToolchainApiIssueGuidance:
+    """ToolchainApiSection should include Issue creation guidance."""
+
+    def test_has_issue_creation_section(self):
+        source_file = PROJECT_ROOT / "src" / "daemon" / "toolchain_handler.py"
+        source = source_file.read_text()
+        assert "需要创建 Issue 时" in source
+        assert "/issues" in source
+        assert "jiangwei-infra" in source
+        assert "type/infrastructure" in source
+
+    def test_issue_body_template_mentions_required_fields(self):
+        source_file = PROJECT_ROOT / "src" / "daemon" / "toolchain_handler.py"
+        source = source_file.read_text()
+        assert "错误来源" in source
+        assert "判断依据" in source
+
+
+class TestRedFlagsInfrastructure:
+    """Red Flags should include the 'not my code' entry."""
+
+    def test_has_infrastructure_red_flag(self):
+        source_file = PROJECT_ROOT / "src" / "daemon" / "toolchain_handler.py"
+        source = source_file.read_text()
+        assert "不是我代码的问题" in source
+        assert "基础设施问题" in source