W17: extract ai_common shared module + fix anthropic data race + brace bugs

- New plugins_upper/ai_common/ static library: shared PluginConfig, ToolCallAccum,
  StreamContext, secure_zero, extract_host_port, serialize_tool_calls, free_chat_result
- Refactored openai/anthropic plugins to use dstalk_ai:: namespace from ai_common
- Fixed anthropic g_config raw pointer → std::atomic (data race)
- Added SSE parse error counter with threshold abort (kMaxSseParseErrors=5)
- Fixed missing closing brace in both plugins' error-body catch block
- Updated test targets: ai_common include path + link, using namespace dstalk_ai
- plugin_loader_test: added stub_unreg + service_registry.cpp for unregister_service
- Includes pre-existing uncommitted changes from prior waves

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/ci-build.bat

@@ -7,17 +7,80 @@ set BUILD_DIR=%PROJECT_DIR%\build
 echo === dstalk CI Build ===
 echo Project: %PROJECT_DIR%
 
-if not exist "%BUILD_DIR%" mkdir "%BUILD_DIR%"
-cd /d "%BUILD_DIR%"
-
-echo --- CMake Configure ---
-cmake "%PROJECT_DIR%" -G Ninja -DCMAKE_BUILD_TYPE=Release -DDSTALK_BUILD_TESTS=ON -DDSTALK_BUILD_GUI=OFF
+:: --- Find vcvarsall.bat for MSVC environment ---
+set VCVARSALL=
+for %%d in (
+    "C:\Program Files\Microsoft Visual Studio\2022\Enterprise"
+    "C:\Program Files\Microsoft Visual Studio\2022\Professional"
+    "C:\Program Files\Microsoft Visual Studio\2022\Community"
+    "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise"
+    "C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional"
+    "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community"
+) do (
+    if exist "%%~d\VC\Auxiliary\Build\vcvarsall.bat" (
+        set "VCVARSALL=%%~d\VC\Auxiliary\Build\vcvarsall.bat"
+        goto :found_vcvars
+    )
+)
+:found_vcvars
+if "%VCVARSALL%"=="" (
+    echo ERROR: vcvarsall.bat not found - install Visual Studio or set VCVARSALL
+    exit /b 1
+)
+echo Using vcvarsall: %VCVARSALL%
+call "%VCVARSALL%" x64
 if errorlevel 1 exit /b 1
 
+:: --- Find conan: prefer tools\ local install, fallback to PATH ---
+set CONAN=
+if exist "%PROJECT_DIR%\tools\.venv\Scripts\conan.exe" (
+    set "CONAN=%PROJECT_DIR%\tools\.venv\Scripts\conan.exe"
+) else (
+    where conan >nul 2>&1
+    if not errorlevel 1 set "CONAN=conan"
+)
+if "%CONAN%"=="" (
+    echo ERROR: conan not found in tools\ or PATH
+    exit /b 1
+)
+echo Using conan: %CONAN%
+
+:: --- Detect conan profile ---
+echo --- Conan Profile Detect ---
+"%CONAN%" profile detect --force
+if errorlevel 1 exit /b 1
+
+:: --- Install dependencies ---
+echo --- Conan Install ---
+if not exist "%BUILD_DIR%" mkdir "%BUILD_DIR%"
+cd /d "%BUILD_DIR%"
+"%CONAN%" install "%PROJECT_DIR%\deps\" --build=missing -s build_type=Release
+if errorlevel 1 exit /b 1
+
+:: --- Find conan toolchain ---
+set TOOLCHAIN=
+if exist "%BUILD_DIR%\build\Release\generators\conan_toolchain.cmake" (
+    set "TOOLCHAIN=%BUILD_DIR%\build\Release\generators\conan_toolchain.cmake"
+) else if exist "%BUILD_DIR%\Release\generators\conan_toolchain.cmake" (
+    set "TOOLCHAIN=%BUILD_DIR%\Release\generators\conan_toolchain.cmake"
+)
+if "%TOOLCHAIN%"=="" (
+    echo ERROR: conan_toolchain.cmake not found
+    exit /b 1
+)
+echo Toolchain: %TOOLCHAIN%
+
+:: --- CMake configure ---
+echo --- CMake Configure ---
+cmake "%PROJECT_DIR%" -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE="%TOOLCHAIN%" -DDSTALK_BUILD_TESTS=ON -DDSTALK_BUILD_GUI=OFF
+if errorlevel 1 exit /b 1
+
+:: --- Build ---
 echo --- Build ---
 cmake --build . --parallel
 if errorlevel 1 exit /b 1
 
+:: --- Test ---
 echo --- Test ---
 ctest --output-on-failure --parallel 4
 if errorlevel 1 exit /b 1