In CI, git is in detached HEAD state, so git rev-parse returns 'HEAD'.
Use GITHUB_REF and GITHUB_BASE_REF to properly detect release branches
in GitHub Actions workflows.
This ensures pre-commit hooks in CI can correctly identify when running
against release branches and set the appropriate UV index URLs.
Replace isolated UV configuration with unified wrapper script that:
- Detects release branches (release-X.Y.x pattern)
- Checks upstream target branch for feature branches
- Supports LLAMA_STACK_RELEASE_MODE env var for local testing
- Wraps all uv commands (lock, run) in local hooks
When on/targeting release branches, automatically sets:
- UV_EXTRA_INDEX_URL=https://test.pypi.org/simple/
- UV_INDEX_STRATEGY=unsafe-best-match
For local testing on feature branches targeting release branches:
LLAMA_STACK_RELEASE_MODE=true pre-commit run --all-files
This ensures RC versions can be resolved from test.pypi in both
CI (on actual release branches) and local development.
