Update Conan setup to use Python venv.

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

build.bat

@@ -22,8 +22,9 @@ if not exist "%TOOLS%llvm\bin\clang.exe" (
     echo   [ERROR] LLVM/Clang 未找到，请先运行: tools\setup.bat
     pause & exit /b 1
 )
-if not exist "%TOOLS%conan2\conan.exe" (
+if not exist "%TOOLS%.venv\Scripts\conan.exe" (
     echo   [ERROR] Conan2 未找到，请先运行: tools\setup.bat
+    echo   需要已安装 Python 3.10+
     pause & exit /b 1
 )
 
@@ -66,17 +67,15 @@ cd /d "%ROOT%"
 :: ============================================================
 :: 5. Conan 安装依赖
 :: ============================================================
-if not exist "%ROOT%build\conan_toolchain.cmake" (
-    echo [dstalk] Conan 安装依赖...
-    call "%TOOLS%conan2\conan.exe" install deps/ -of build --build=missing
-    if !errorlevel! neq 0 (
-        echo   [ERROR] Conan 安装失败
-        pause & exit /b 1
-    )
-) else (
-    echo [dstalk] Conan 依赖已就绪
+echo [dstalk] Conan 安装/刷新依赖...
+call "%TOOLS%.venv\Scripts\conan.exe" install deps/ -of build --build=missing -s compiler.cppstd=20 -c tools.cmake.cmaketoolchain:generator=Ninja
+if !errorlevel! neq 0 (
+    echo   [ERROR] Conan 安装失败
+    pause & exit /b 1
 )
 
+set "CONAN_GENERATORS=%ROOT%build\build\Release\generators"
+
 :: ============================================================
 :: 6. CMake 配置 + Ninja 编译
 :: ============================================================
@@ -84,7 +83,8 @@ echo [dstalk] CMake 配置 + 编译...
 "%TOOLS%cmake\bin\cmake.exe" -S "%ROOT%" -B "%ROOT%build" -G Ninja ^
   -DCMAKE_C_COMPILER="%TOOLS%llvm\bin\clang.exe" ^
   -DCMAKE_CXX_COMPILER="%TOOLS%llvm\bin\clang++.exe" ^
-  -DCMAKE_TOOLCHAIN_FILE="%ROOT%build\conan_toolchain.cmake" ^
+  -DCMAKE_TOOLCHAIN_FILE="%CONAN_GENERATORS%\conan_toolchain.cmake" ^
+  -DCMAKE_PREFIX_PATH="%CONAN_GENERATORS%" ^
   -DCMAKE_BUILD_TYPE=Release
 if !errorlevel! neq 0 (
     echo   [ERROR] CMake 配置失败