docs: tell agents to fill in the PR template

[davidberenstein1957]

Description

Adds an "Opening Pull Requests" section to docs/how-to/agent-instructions.md. It tells coding agents to fill in every section of .github/PULL_REQUEST_TEMPLATE.md and pass it with gh pr create --body-file, because a plain --body skips the template. It also says the AI Usage Disclosure choice belongs to the human contributor.

Related Issue

N/A. This follows a review comment asking that PRs opened with Claude Code follow the template.

Motivation and Context

My recent PRs were opened by Claude Code with gh pr create --body, which bypasses the template, so none of them followed it. The comment suggested docs/how-to/agents.md, but that page is the tutorial on tracking LLM inference emissions. The file agents actually read is agent-instructions.md: CLAUDE.md, AGENTS.md and .github/copilot-instructions.md all symlink to it. This PR itself was opened following the new instruction.

How Has This Been Tested?

Docs-only change of four lines. I checked that the symlinks resolve to the edited file (ls -l CLAUDE.md AGENTS.md .github/copilot-instructions.md).

Screenshots (if appropriate):

N/A

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Docs only.

AI Usage Disclosure

Please refer to docs/how-to/ai-policy.md for detailed guidelines on how to disclose AI usage in your PR. Accurately completing this section is mandatory.

• 🟥 AI-vibecoded: You cannot explain the logic. Car analogy : the car drive by itself, you are outside it and just tell it where to go.
• 🟠 AI-generated: Car analogy : the car drive by itself, you are inside and give instructions.
• ⭐ AI-assisted. Car analogy : you drive the car, AI help you find your way.
• ♻️ No AI used. Car analogy : you drive the car.

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the docs/how-to/contributing.md document.
• I have added tests to cover my changes.
• All new and existing tests passed.

🤖 Generated with Claude Code

[inimaz]

Thanks @davidberenstein1957 !