docs(guardrails): enforce JSDoc on every new or modified function

Author: PierreBrisorgueil

.github/copilot-instructions.md

@@ -37,6 +37,7 @@ Use `.github/prompts/*.prompt.md` for guided workflows:
 - Avoid risky renames or moves of core stack paths used by downstream merges
 - Keep changes minimal and merge-friendly for downstream projects
 - Flag security or mergeability risks explicitly in reviews
+- Every new or modified function must have a JSDoc header: one-line description, `@param` for each argument, `@returns` if the function returns a value
 
 ## Architecture and modularity
 

ERRORS.md

@@ -11,3 +11,4 @@ Use this file as a compact memory of recurring AI mistakes.
 
 ## Entries
 
+- [2026-02-22] functions: added functions without JSDoc header -> always add JSDoc (description + @param + @returns)