docs: add validation rule - always validate after changes

memory/2026-02-14.md

@@ -154,3 +154,15 @@ This script was periodically overwriting count.txt with nginx log line count, ov
 
 **Lesson:** Check for competing scripts before implementing fixes.
 
+
+---
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+## Rule Added - Feb 14, 2026
+**Always validate after changes.** No exceptions.
+- Test functionality
+- Verify file integrity  
+- Check permissions
+- Confirm expected output
+
+Applied retroactively to today’s counter fix.
+