update-pr-description

## Pre-requisites - gh CLI: !`which gh` **If the gh CLI is not found:** - Inform the user that it needs to be installed and configured before this skill can be used - **Immediately stop** execution of this skill, as it cannot be executed ## Project Context - current branch: !`git branch --show-current` - default branch: !`git symbolic-ref --short refs/remotes/origin/HEAD` - branch summary: !`git log origin/HEAD..HEAD --oneline` - branch stats: !`git diff origin/HEAD...HEAD --stat` - branch changes: !`git diff origin/HEAD...HEAD` ## Step 1: Validate Branch State Before generating a PR description, verify the branch has content to describe: 1. **If `default branch` is empty** — `origin/HEAD` is not set. Use `AskUserQuestion` to ask the user for the default branch name (e.g., `main`, `master`, `develop`). Use that branch as the base for all git commands in subsequent steps. 2. **If `branch summary` is empty** — there are no commits on this branch relative to the default branch. Inform the user and stop. 3. **If `branch stats` is empty** — there are no file changes despite having commits (e.g., empty commits or fully reverted changes). Inform the user and stop. ## Step 2: Analyze Changes Review the branch diff, commits, and relevant source code to understand the PR. Identify the central mechanism — the primary purpose of the PR. If the PR is about feature flags, migrations, or behavioral changes, those ARE the point, not a side detail. Classify the change type (new fea...