chore(memory): L0 line-1 convention — all files start with L0 summary

Migrated all memory files to have L0 comment as first line,
consistent with upstream PAI convention.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

memory/personal/action-items.md

@@ -1,5 +1,5 @@
-# Personal — Action Items
 <!-- L0: Open and completed tasks -->
+# Personal — Action Items
 
 <!-- Format: - [ ] task | due:YYYY-MM-DD | pri:high/medium/low | added:YYYY-MM-DD -->