Update copilot-instructions.md (#15032)

Co-authored-by: Vineeth <[email protected]>

Author: anupriya13

.github/copilot-instructions.md

@@ -36,6 +36,8 @@ React Native Windows is a Microsoft-maintained implementation of React Native th
 
 ### C++ Code (.cpp, .h files)
 
+- While raising a PR don't do any changes in vnext/codegen directory, that directory should be untouched.
+
 **Style Guide**: Follow the project's `.clang-format` configuration
 - **Line length**: 120 characters maximum
 - **Indentation**: 2 spaces, no tabs
@@ -185,6 +187,8 @@ yarn change --type prerelease
 
 These commands ensure code quality, consistent formatting, and proper change tracking for the monorepo versioning system.
 
+Delete the PR branch "colpilot/fix-*" once the copilot PR is merged or closed to maintain repo hygiene.
+
 ### Native Module Development
 
 **C++ Native Module Pattern**:
@@ -289,4 +293,4 @@ class SampleViewManager : public ViewManagerBase {
 - Include usage examples for complex APIs
 - Explain Windows-specific behavior differences
 
-This guidance helps ensure consistent, high-quality contributions to React Native Windows while leveraging platform-specific capabilities effectively.
+This guidance helps ensure consistent, high-quality contributions to React Native Windows while leveraging platform-specific capabilities effectively.