Fix release workflow failure caused by setup-uv cache post-step

[Copilot]

The release workflow run failed in the publish job even though package upload succeeded. The failure was triggered by setup-uv post-job cache handling when no cache path was created in that job context.

• Root cause

  • publish failed on Post Set up Python + uv due to missing cache directory (/home/runner/work/_temp/setup-uv-cache), not during PyPI publish itself.

• Workflow changes

  • Disabled setup-uv caching in release jobs that do not need dependency caching:
    • publish
    • mark-release
  • Scope is intentionally limited to _release.yml; build/test job behavior is unchanged.

• Representative change

  - name: Set up Python + uv ${{ env.UV_VERSION }}
    uses: astral-sh/setup-uv@v7
    with:
      version: ${{ env.UV_VERSION }}
      python-version: ${{ env.PYTHON_VERSION }}
      enable-cache: false