Module pr 

GitHub PR helpers using the gh CLI.

Responsibilities:

• Create PRs for worker branches and return structured metadata.
• Merge PRs using a chosen merge method.
• Query PR mergeability state.

Not handled here:

• Task selection or worker execution (see commands::run::parallel).
• Direct-push parallel integration logic (see commands::run::parallel::integration).

Invariants/assumptions:

• gh is installed and authenticated.
• Repo root points to a GitHub-backed repository.