create-pr-github-gitlisted

Create a GitHub pull request from the current branch, deriving the title and description from the branch's git history. Steps: 1. Check that `gh` is installed and authenticated by running `gh auth status`. If not, tell the user and stop. 2. Get the repo's default branch: `gh repo view --json defaultBranchRef --jq '.defaultBranchRef.name'`. Use this as the base for all comparisons below (referred to as `<base>`). 3. Push the current branch to the remote if needed: - Run `git rev-parse --abbrev-ref --symbolic-full-name @{upstream}` to check if an upstream is set. - If no upstream is set, run `git push -u origin HEAD` to push and set tracking. - If an upstream is set, run `git push` to make sure the remote is up to date. 4. Run `git log --oneline <base>..HEAD` to list commits on this branch. 5. Run `git diff <base>...HEAD --stat` to understand what changed. 6. Derive a PR title (imperative tense, under 72 chars) and description from the commits and diff: - What changed (2-4 sentences, plain English) - Why it was needed if inferrable - Notable implementation details as bullet points (optional) - No filler like "This PR..." or vague words without specifics 7. Check if a PR already exists for this branch: `gh pr view --json url,number 2>/dev/null`. - If no PR exists, run `gh pr create --title "<title>" --body "<description>"` to open one. Append any user-provided flags from $ARGUMENTS. - If a PR already exists, run `gh pr edit --title "<title>" --body "<