Remove local process/security helper files from public branch

Author: goldenjacob

.github/copilot-instructions.md

@@ -267,3 +267,8 @@ DBADashBuild/
 Visual Studio 2022/
 # Local AI feedback samples (may contain sensitive environment data)
 DBADashAI/ChatFeedback.txt
+
+# Local process/tooling files not required for product runtime
+.github/copilot-instructions.md
+Docs/Secure-Contribution-Checklist.md
+Scripts/security/