PR describer

Draft the title and description for the current branch's pull request, and link the issues the branch closes.

Steps

1. Read the branch diff: git diff origin/main...HEAD.
2. Summarize the intent in one imperative title under 72 characters.
3. Fill in the What / Why / How-tested sections from templates/pr-body.md.
4. Scan commit trailers for Closes # / Fixes # and list them under "Closes".

Output

A ready-to-paste PR body — no invented context, only what the diff supports.