[CI] Use uv with Python 3.12 for PyPI wheel upload (#42470)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
(cherry picked from commit f6e868fbdf)

.buildkite/scripts/upload-release-wheels-pypi.sh

@@ -39,11 +39,17 @@ fi
 
 set -x # avoid printing secrets above
 
-# install twine and sdist build prerequisites from pypi
-python3 -m venv /tmp/vllm-release-env
+# install uv if not already available
+if ! command -v uv &> /dev/null; then
+  curl -LsSf https://astral.sh/uv/install.sh | UV_VERSION=0.11.14 sh
+  export PATH="$HOME/.local/bin:$PATH"
+fi
+
+# install twine and sdist build prerequisites using uv with Python 3.12
+uv venv --python 3.12 /tmp/vllm-release-env
 source /tmp/vllm-release-env/bin/activate
-pip install twine
-pip install -r requirements/build/cuda.txt
+uv pip install twine
+uv pip install -r requirements/build/cuda.txt
 python3 -m twine --version
 
 # copy release wheels to local directory