[Feature Request] Use PR template in "Commit and Create PR" flow

What variant of Codex are you using?

App

What feature would you like to see?

Currently, the "Commit and Create PR" button creates a pull request without applying any pull request template. This results in PRs with inconsistent or missing information from contributors, making it harder to review changes efficiently.

Problem
When a PR is created via the single-button "Commit and Create PR" flow, the PR body is left blank — bypassing any .github/pull_request_template.md that may exist in the repository. This means contributors aren't prompted to fill in key details like:

• Description of changes
• Type of change (bug fix, feature, refactor, etc.)
• Testing steps taken
• Related issues or references

Suggested Fix

1. Add a default .github/pull_request_template.md to the openai/codex repository.
2. Update the "Commit and Create PR" flow to pre-populate the PR body using this template — consistent with how GitHub natively uses PR templates when a PR is opened via the web UI.

This would ensure contributors provide structured and relevant context with every pull request, reducing back-and-forth during review.

Additional information

GitHub's PR creation API supports pre-filling the body field. The template content can be read from .github/pull_request_template.md at the time the PR is created and passed directly as the body parameter — no extra user intervention required beyond filling in the template sections.