fix(errors): align ERRORS.md JSDoc rule with guardrail nuance (non-void + async)

Author: PierreBrisorgueil

ERRORS.md

@@ -11,5 +11,5 @@ Use this file as a compact memory of recurring AI mistakes.
 
 ## Entries
 
-- [2026-02-22] functions: new or modified functions without JSDoc header -> always add JSDoc (description + `@param` + `@returns`)
+- [2026-02-22] functions: new or modified functions without JSDoc header -> always add JSDoc (description + `@param` for each arg + `@returns` for non-void return values and all async functions)
 - [2026-02-22] tests: never patch code to pass a test -> if a test is wrong, fix the test; if logic needs refactoring, refactor it