enable python unit test (#15593)

* enable python unit test

* fix Windows

* Require numpy for the plugin tests in CI

.github/workflows/unit_tests.yml

@@ -44,6 +44,14 @@ jobs:
         uses: actions/download-artifact@v8
         with:
           name: ${{ inputs.artifact }}
+      # run_unit_tests.sh installs the plugin tests' numpy with the uv the build stages
+      # beside them; the Windows arm64 build bundles none, so put one on PATH there.
+      - name: Install uv
+        if: runner.os == 'Windows' && runner.arch == 'ARM64'
+        uses: astral-sh/setup-uv@v10.2.0
+        with:
+          version: "0.11.21"  # ORCA_UV_VERSION in CMakeLists.txt
+          enable-cache: false
       - uses: lukka/get-cmake@latest
         with:
           cmakeVersion: "~4.3.0"  # use most recent 4.3.x version