Step 0: Prerequisites & Base Branch Detection

Before doing anything else, verify the environment can support this workflow. These checks prevent confusing failures mid-run.

Git repo check: Run git rev-parse --git-dir. If it fails, abort: "Not a git repository."
gh CLI check: Run gh auth status. If it fails, warn: "gh CLI is not authenticated — PR-related steps (body update, base branch detection via PR) will be skipped. Falling back to git-only detection." Continue the workflow but skip PR body updates in Step 9.
Clean working tree check: Run git status --porcelain (never use -uall). If there are uncommitted changes to documentation files (.md, VERSION, CHANGELOG*), warn the user: "You have uncommitted changes to doc files that may conflict with this workflow. Continue anyway?" via AskUserQuestion.

Then determine which branch this PR targets. Use the result as "the base branch" in all subsequent steps.

document-release