Add the guidance prompt only

[Copilot]

This change now only adds a concise guidance prompt for GitHub Copilot workflows.

• Guidance prompt update

  • Updates .github/copilot-instructions.md with a small prompt section that tells agents to:
    • read AGENTS.md before generating, refactoring, or reviewing code
    • make the smallest correct change and preserve existing structure
    • surface conflicts, missing requirements, or ambiguity instead of guessing
    • keep outputs machine-readable with short bullets, numbered steps, and fenced code blocks
    • include exact validation commands and results before requesting review

• Scope correction

  • Removes the previously added guidance scaffold, implementation files, tests, and related documentation changes so the PR contains only the requested prompt update

Validation:

pre-commit run --all-files

Passed

[DapengFeng]

@copilot just generate the guidance prompt only, remove additional files.

[Copilot]

@copilot just generate the guidance prompt only, remove additional files.

Updated in b43ebf8. The extra scaffold files, tests, and docs were removed, and the PR now keeps only the guidance prompt in .github/copilot-instructions.md. No UI changes were involved.