Move to .github/copilot-instructions.md with minimal prompt

.ai-instructions.md

@@ -1,47 +0,0 @@
-# AI Assistant Instructions for 3D Print Meetup Repository
-
-## Important Guidelines for AI Assistants
-
-### Character Usage Rules
-
-**NEVER use the unicode multiplication symbol (×) in any documentation.**
-
-- ❌ WRONG: `25mm × 25mm × 25mm`
-- ✅ CORRECT: `25mm x 25mm x 25mm`
-
-**Always use lowercase 'x' for dimensions, not the unicode × (U+00D7) character.**
-
-This applies to:
-
-- Challenge documentation
-- Wiki pages
-- README files
-- Any markdown documentation
-- Announcements
-- All text content
-
-### Reason
-
-The unicode × character can cause display issues in:
-
-- Email clients
-- Reddit posts
-- Various text editors
-- Screen readers
-- Plain text environments
-
-Using lowercase 'x' ensures universal compatibility across all platforms where this content will be shared.
-
-### Quick Check
-
-Before committing any files, search for the × character and replace with lowercase x.
-
-PowerShell command to check:
-
-```powershell
-Get-ChildItem -Recurse -Include *.md | Select-String "×"
-```
-
----
-
-**Last Updated**: October 28, 2025

.github/copilot-instructions.md

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+# GitHub Copilot Instructions
+
+**Never use the unicode multiplication symbol (×, U+00D7) in any documentation, code, or markdown.**
+
+Always use a plain lowercase 'x' for dimensions and multiplication.
+
+- WRONG: `25mm × 25mm × 25mm`
+- CORRECT: `25mm x 25mm x 25mm`