Tool for creating pull request should instruct LLMs to follow PULL_REQUEST_TEMPLATE.md

[digitarald]

Describe the bug

Agents currently create pull requests without looking at the pull request template that's in the repo folder.

Expected vs actual behavior

The PR creation tool should recommend the use of PULL_REQUEST_TEMPLATE.md as reference before creating the pull request description content. This way any pull requests follow the same UI flow that GitHub provides.

cc @pamelafox

[almaleksia]

I think it's going to be a good case for server instructions.

[mattdholloway]

Closed by #1442