Snapshot PR

A PR description is a snapshot: one glance gives the reviewer the whole picture. A concise description is kindness to the people who review your work.

Gather

Know the whole change before writing a word:

1. Find where the branch forked: git merge-base HEAD <default-branch> (default branch via gh repo view --json defaultBranchRef).
2. Read the full diff and commit messages since the merge base.
3. If a PR already exists (gh pr view), read its current description and review comments. If the description is already a snapshot (matches the template below), jump to Update below. If it isn't, rewrite it with Write, keeping facts from the old description that are still true — and never dropping images or links you can't regenerate.

Done when every changed file is accounted for in your understanding — not necessarily in the description.

Write

Use exactly this template. Omit sections that don't apply. Never add top-level sections (the ## headers are fixed; content nested under them, like Flow's diagram and Under the hood note, is not a new section).