[copilot] Extract copilot instructions updates from PR 30291 for handling existing PRs

[Copilot]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Description

This PR extracts the copilot instructions updates from PR #30291 and creates a focused PR containing only those instruction changes, as requested in issue #30297.

Changes Made

Added a new section "Handling Existing PRs for Assigned Issues" to .github/copilot-instructions.md that provides guidance for AI agents on how to handle scenarios where there's already an existing PR for an assigned issue.

New Guidance Includes:

1. Review existing PRs thoroughly - Examine proposed changes, implementation approach, and discussion
2. Provide analysis and opinion - Evaluate whether existing solutions are effective and follow best practices
3. Always include a summary - Document thoughts about other open PRs in PR descriptions
4. Don't force using existing approach - Flexibility to not base work on existing PRs when not confident
5. It's OK to abandon existing PRs - Complete acceptance to implement different solutions when needed
6. Document abandonment reasoning - Clear notes explaining why existing approaches were abandoned
7. Use existing PR as foundation when valid - Build upon solid existing work when confident in the approach
8. Identify improvement opportunities - Areas to enhance like test coverage, code quality, error handling, documentation
9. Build upon, don't duplicate - Extend existing work rather than creating competing solutions

Benefits

• Reduces duplicate effort by encouraging AI agents to review and build upon existing work when appropriate
• Provides flexibility by explicitly allowing abandonment of existing PRs when not confident in the approach
• Improves collaboration by requiring documentation of decisions and reasoning
• Enhances code quality by encouraging comprehensive improvements to existing solutions
• Creates transparency by requiring summaries of other open PRs in descriptions

This guidance will help AI agents make better decisions when assigned to issues that already have open PRs, leading to more efficient development workflows and higher quality outcomes.

Fixes #30297.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[PureWeen]

Don't remove any lines from the instructions

[Copilot]

Don't remove any lines from the instructions

I didn't remove any lines from the instructions file. The changes only added 18 lines (the new "Handling Existing PRs for Assigned Issues" section) without removing any existing content. The git stats show 18 insertions and 0 deletions. Could you clarify what specific lines you're concerned about?