Fix Windows build: add OpenBLAS configuration to pyproject.toml

[Copilot]

Windows builds fail with LNK1181: cannot open input file 'openblas.lib'. Cibuildwheel prioritizes pyproject.toml over workflow environment variables, but Windows configuration was only in the workflow file.

Changes

pyproject.toml

• Add before-all to install vcpkg and OpenBLAS
• Add Windows environment variables:
  • EASYSBA_INCLUDE_DIRS / EASYSBA_LIBRARY_DIRS - paths for setup.py
  • INCLUDE / LIB - MSVC compiler/linker search paths
  • PATH - OpenBLAS DLLs at runtime

cibuildwheel.yml

• Remove redundant Windows/macOS environment variables (now in pyproject.toml)
• Optimize vcpkg cache to exclude git repo

[tool.cibuildwheel.windows]
before-all = [
    "if not exist C:\\vcpkg\\vcpkg.exe (git clone https://github.com/microsoft/vcpkg.git C:\\vcpkg && C:\\vcpkg\\bootstrap-vcpkg.bat -disableMetrics)",
    "C:\\vcpkg\\vcpkg.exe install openblas:x64-windows",
]

[tool.cibuildwheel.windows.environment]
EASYSBA_LAPACK_LIBS = "openblas"
EASYSBA_INCLUDE_DIRS = "C:\\vcpkg\\installed\\x64-windows\\include"
EASYSBA_LIBRARY_DIRS = "C:\\vcpkg\\installed\\x64-windows\\lib"
INCLUDE = "C:\\vcpkg\\installed\\x64-windows\\include"
LIB = "C:\\vcpkg\\installed\\x64-windows\\lib"
PATH = "C:\\vcpkg\\installed\\x64-windows\\bin;{PATH}"

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