fix(github): trust a bot on its own commit in the repository - #35

The new tests exercise the bot trust checks and no actionable issues remain.

This pull request allows a GitHub App bot to count as trusted when its pull request targets a branch in the same repository and the head commit is attributed to that bot; otherwise the existing association and permission checks remain in place. It carries the pull-request and commit metadata through the GitHub client and approval guard, and adds coverage for same-repository versus fork detection, commit attribution, and lookup failures.