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 -->
 

memory/personal/entities.md

@@ -1,4 +1,4 @@
-# Personal — Entities
 <!-- L0: People, places, and things -->
+# Personal — Entities
 
 <!-- Edit in place by ### Name header. -->

memory/personal/hot-memory.md

@@ -1,4 +1,4 @@
-# Personal — Hot Memory
 <!-- L0: Current state and top-of-mind for personal life -->
+# Personal — Hot Memory
 
 <!-- Rewrite freely. Keep under 50 lines. -->

memory/personal/observations.md

@@ -1,4 +1,4 @@
-# Personal — Observations
 <!-- L0: Timestamped observations and events -->
+# Personal — Observations
 
 <!-- Append-only. Format: - YYYY-MM-DD [tags]: observation -->