Fix source: not found error in test-cuda workflow

[Copilot]

GitHub Actions defaults to sh for run blocks, which doesn't include source as it's a bash builtin. The "Install Python" step in test-cuda.yaml was failing with exit code 127 as a result.

Change

Added shell: bash to the "Install Python" step:

- name: Install Python
  shell: bash
  run: |
    uv venv --python ${{ matrix.pyver }}
    source .venv/bin/activate

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[Copilot]

Pull request overview

This PR fixes a GitHub Actions workflow failure in the CUDA test build by ensuring the Install Python step runs under bash, so the source builtin is available inside the containerized job environment.

Changes:

• Set shell: bash for the “Install Python” step in the CUDA workflow to avoid source: not found (exit code 127).

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