create-pr

Determine TARGET_BRANCH:

• If the user named a branch, use it.
• If the user said "ship it", "open a PR", or similar without naming a branch, default to the repository's main branch — detect it rather than assuming the name:

git symbolic-ref --short refs/remotes/origin/HEAD 2>/dev/null | sed 's|^origin/||' \
  || echo main

• Only ask when the repo has several plausible integration branches (for example both develop and main receive feature work) and the intent is genuinely ambiguous:

"Which branch should this PR target? (for example dev, staging, or main)"