add learnings switch to instructions file

Author: eleanorjboyd

.github/prompts/new-test-guide.prompt.md …tructions/new-test-guide.instructions.md.github/prompts/new-test-guide.prompt.md renamed to .github/instructions/new-test-guide.instructions.md .github/prompts/new-test-guide.prompt.md renamed to .github/instructions/new-test-guide.instructions.md

@@ -1,5 +1,5 @@
 ---
-mode: agent
+applyTo: '**'
 ---
 
 # Testing Guide: Unit Tests and Integration Tests
@@ -490,3 +490,5 @@ You know you have good integration tests when:
 12. **Name test suites clearly** - use descriptive `suite()` names that work well with grep filtering
 
 ## Learnings
+
+-   Always use dynamic path construction with Node.js `path` module when testing functions that resolve paths against workspace folders to ensure cross-platform compatibility (1)