fix Windows vcpkg path in CI (backslash escaping issue)

CIBW_ENVIRONMENT_WINDOWS values are parsed by shlex, which treats
backslashes as escape characters. Use forward slashes instead —
Windows accepts them and they survive shlex parsing.

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

Author: Transurgeon

.github/workflows/build-and-publish.yml

@@ -66,7 +66,7 @@ jobs:
           CIBW_ARCHS_LINUX: "auto aarch64"
           CIBW_BEFORE_BUILD_LINUX: "yum install -y openblas-devel || apt-get install -y libopenblas-dev"
           CIBW_BEFORE_BUILD_WINDOWS: "vcpkg install openblas:x64-windows"
-          CIBW_ENVIRONMENT_WINDOWS: "VCPKG_INSTALLED_DIR=C:\\vcpkg\\installed\\x64-windows"
+          CIBW_ENVIRONMENT_WINDOWS: "VCPKG_INSTALLED_DIR=C:/vcpkg/installed/x64-windows"
 
       - name: Check wheels
         shell: bash