feat: Add virtual environment creation step for Python setup

.gitea/actions/setup-python-env/action.yml

@@ -47,6 +47,32 @@ runs:
         python --version
         python -m pip --version >/dev/null 2>&1 || python -m ensurepip --upgrade
         python -m pip --version
+    - name: Create virtual environment
+      if: ${{ inputs.use-system-python == 'true' }}
+      shell: bash
+      run: |
+        set -euo pipefail
+        if [ -z "${RUNNER_TEMP:-}" ]; then
+          echo "RUNNER_TEMP is not set; cannot create virtual environment" >&2
+          exit 1
+        fi
+        VENV_PATH="$(mktemp -d "${RUNNER_TEMP%/}/ci-venv-XXXXXX")"
+        python -m venv "${VENV_PATH}"
+        PATH_ENTRY=""
+        if [ -f "${VENV_PATH}/bin/activate" ]; then
+          PATH_ENTRY="${VENV_PATH}/bin"
+        elif [ -f "${VENV_PATH}/Scripts/activate" ]; then
+          PATH_ENTRY="${VENV_PATH}/Scripts"
+        else
+          echo "Unable to locate virtual environment scripts" >&2
+          exit 1
+        fi
+        export PATH="${PATH_ENTRY}:${PATH}"
+        echo "${PATH_ENTRY}" >> "${GITHUB_PATH}"
+        echo "VIRTUAL_ENV=${VENV_PATH}" >> "${GITHUB_ENV}"
+        # Re-evaluate the python binary for subsequent steps
+        python --version
+        python -m pip --version
     - name: Configure apt proxy
       shell: bash
       run: |