W20: Tool Calling 闭环 + Stream+Tools + 回归测试 + session auto-save + ASan CI (W20.1-W20.6)

- W20.1: CLI tool_calls→execute→result→re-call 循环（5轮上限）
- W20.2: deepseek 流式 tool_calls 增量解析（configure 缓存，无 ABI break）
- W20.3: plugin_loader 回归测试 5 块 32 断言（路径/原子性/mock 日志）
- W20.4: plugin_loader ABI 契约校验（name/version/on_init 字段验证）
- W20.5: ASan/UBSan CMake preset + CI sanitizer job（PR-only Linux）
- W20.6: session auto-save（on_shutdown 写 %APPDATA%/dstalk/session.json）

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

tests/CMakeLists.txt

@@ -87,3 +87,39 @@ target_link_libraries(dstalk-context-plugin-test
 )
 
 add_test(NAME dstalk-context-plugin-test COMMAND dstalk-context-plugin-test)
+
+# ============================================================
+# dstalk-plugin-loader-test — PluginLoader 安全回归测试
+# W20.3 (qa-xu): 覆盖 W19 F-18.3-1~5 修复验证
+# ============================================================
+
+add_executable(dstalk-plugin-loader-test
+    plugin_loader_test.cpp
+    ${CMAKE_SOURCE_DIR}/dstalk-core/src/plugin_loader.cpp
+    ${CMAKE_SOURCE_DIR}/dstalk-core/src/boost_json.cpp
+)
+
+target_include_directories(dstalk-plugin-loader-test
+    PRIVATE ${CMAKE_SOURCE_DIR}/dstalk-core/src
+)
+
+target_compile_features(dstalk-plugin-loader-test
+    PRIVATE cxx_std_17
+)
+
+find_package(Boost REQUIRED CONFIG)
+
+target_compile_definitions(dstalk-plugin-loader-test
+    PRIVATE
+        BOOST_JSON_HEADER_ONLY
+        BOOST_ALL_NO_LIB
+        DSTALK_TEST_PLUGINS_DIR="${CMAKE_BINARY_DIR}/plugins"
+)
+
+target_link_libraries(dstalk-plugin-loader-test
+    PRIVATE
+        dstalk
+        boost::boost
+)
+
+add_test(NAME dstalk-plugin-loader-test COMMAND dstalk-plugin-loader-test)