Refactor to plugin architecture with B3 CLI UX, C2 smoke tests, C3 CI scripts

Architecture overhaul (Wave 1-4 collaborative work):
- Migrated dstalk-core from monolithic api.cpp to plugin-based design with
  host/service_registry/event_bus/plugin_loader and topological initialization.
- Split public headers into dstalk_host.h / dstalk_services.h /
  dstalk_lsp.h / dstalk_types.h; deleted obsolete dstalk_api.h and inlined
  TLS/file/net code now provided by plugins.
- Added 9 plugins: deepseek, anthropic, network, session, context, tools,
  config, file-io, lsp; AI plugins register as "ai.<provider>" services.

B3 CLI interaction enhancement:
- Prompt now shows current model name (A1).
- /status command prints model/base_url/api_key (sanitized: shown only
  as set/unset)/services readiness (A2).
- SIGINT/Ctrl+C handled on POSIX (signal) and Windows (SetConsoleCtrlHandler);
  /quit no longer std::exit(0) but sets a quit flag so dstalk_shutdown runs
  exactly once via natural control flow (B1+B2).
- Cross-DLL free fixed: print_file uses dstalk_free instead of std::free (B4).
- --batch mode plus isatty auto-detection for piped stdin (C1).
- fgets truncation detection with friendly error and stdin draining (C3).
- Distinct exit codes (init/AI/service-unavailable) (C4).
- /model rejects empty model name (C5).

C2 smoke test extension:
- 4 new test blocks: null-safety (file_io/session/tools/config),
  escape-boundary round-trip, tools->execute call chain, session robustness
  (add(nullptr), clear -> token_count == 0).

C3 CI build scripts:
- scripts/ci-build.sh and scripts/ci-build.bat invoke cmake configure +
  parallel build + ctest, suitable for GitHub Actions.

Build verified: dstalk-cli compiles, smoke test passes via ctest.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

dstalk-core/CMakeLists.txt

@@ -1,16 +1,17 @@
 # ============================================================
-# dstalk-core — 核心 DLL
-# 包含: 网络通讯 / AI接口 / 文件读写
+# dstalk-core — 核心 DLL (插件宿主)
+# 包含: 插件管理 / 服务注册 / 事件总线 / 配置存储
 # ============================================================
 
 find_package(Boost REQUIRED CONFIG)
 find_package(OpenSSL REQUIRED CONFIG)
 
 add_library(dstalk SHARED
-    src/api.cpp
-    src/file/file_io.cpp
-    src/net/http_client.cpp
-    src/ai/deepseek_api.cpp
+    src/host.cpp
+    src/config_store.cpp
+    src/event_bus.cpp
+    src/service_registry.cpp
+    src/plugin_loader.cpp
     src/boost_json.cpp
 )
 
@@ -25,6 +26,11 @@ target_link_libraries(dstalk
         openssl::openssl
 )
 
+# dlopen / dlclose / dlsym on Linux and macOS
+if(NOT WIN32)
+    target_link_libraries(dstalk PRIVATE ${CMAKE_DL_LIBS})
+endif()
+
 # 导出 DLL 符号宏
 target_compile_definitions(dstalk
     PRIVATE