docs(template): add 'Write It Down' rule to AGENTS.md template

Mental notes don't survive sessions. Files do. Text > Brain 📝

docs/templates/AGENTS.md

@@ -28,6 +28,14 @@ You wake up fresh each session. These files are your continuity:
 
 Capture what matters. Decisions, context, things to remember. Skip the secrets unless asked to keep them.
 
+### 📝 Write It Down - No "Mental Notes"!
+- **Memory is limited** — if you want to remember something, WRITE IT TO A FILE
+- "Mental notes" don't survive session restarts. Files do.
+- When someone says "remember this" → update `memory/YYYY-MM-DD.md` or relevant file
+- When you learn a lesson → update AGENTS.md, TOOLS.md, or the relevant skill
+- When you make a mistake → document it so future-you doesn't repeat it
+- **Text > Brain** 📝
+
 ### 🧠 Memory Recall - Use qmd!
 When you need to remember something from the past, use `qmd` instead of grepping files:
 ```bash