W22: coverage metric + network tests + Tool stream feedback + stdin pipe + session path + dependency check (W22.1-W22.6)

- W22.1: gcovr 覆盖率度量 + CI coverage job（40% 阈值 warning）
- W22.2: network_plugin 单元测试（parse_headers_json/extract_host_port/SSE/异常保护）
- W22.3: Tool Calling 流式反馈（chat_stream + "[工具调用]/[工具结果]" 状态行）
- W22.4: --prompt stdin pipe（--prompt - 从 stdin 读取）
- W22.5: session 路径健壮化（static 缓存 + mkdir + fallback）
- W22.6: 插件依赖拓扑静态校验（validate_dependencies 循环/缺失检测）

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CMakePresets.json

@@ -74,6 +74,24 @@
                 "CMAKE_C_FLAGS": "-fsanitize=thread -fno-omit-frame-pointer",
                 "CMAKE_CXX_FLAGS": "-fsanitize=thread -fno-omit-frame-pointer"
             }
+        },
+        {
+            "name": "ci-coverage",
+            "displayName": "CI Coverage (gcov/lcov)",
+            "description": "Code coverage Linux clang CI build with --coverage",
+            "generator": "Ninja",
+            "toolchainFile": "${sourceDir}/build/Release/conan_toolchain.cmake",
+            "binaryDir": "${sourceDir}/build/ci-coverage",
+            "cacheVariables": {
+                "CMAKE_POLICY_DEFAULT_CMP0091": "NEW",
+                "CMAKE_BUILD_TYPE": "Release",
+                "CMAKE_C_COMPILER": "clang-18",
+                "CMAKE_CXX_COMPILER": "clang++-18",
+                "CMAKE_C_FLAGS": "--coverage",
+                "CMAKE_CXX_FLAGS": "--coverage",
+                "CMAKE_EXE_LINKER_FLAGS": "--coverage",
+                "CMAKE_SHARED_LINKER_FLAGS": "--coverage"
+            }
         }
     ],
     "buildPresets": [
@@ -96,6 +114,11 @@
             "name": "ci-threadsan",
             "configurePreset": "ci-threadsan",
             "jobs": 0
+        },
+        {
+            "name": "ci-coverage",
+            "configurePreset": "ci-coverage",
+            "jobs": 0
         }
     ],
     "testPresets": [
@@ -129,6 +152,13 @@
             "execution": {
                 "jobs": 0
             }
+        },
+        {
+            "name": "ci-coverage",
+            "configurePreset": "ci-coverage",
+            "execution": {
+                "jobs": 0
+            }
         }
     ]
 }