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/cog-meta/improvements.md

@@ -1,5 +1,5 @@
-# Cog — Improvements
 <!-- L0: Feature ideas, wishlists, and repair notes -->
+# Cog — Improvements
 
 <!-- Edit in place by section. -->