update claude memory

Author: heypoom

config/dot_claude/metabase.md

@@ -4,4 +4,6 @@
 - My local Metabase directory is in `/Users/poom/Workspaces/metabase/metabase`
   - It has the git-excluded `.claude-private` directory which should contain
     the Claude memory files for project planning.
-
+  - `.claude-private/emb-*` (e.g. emb-451) contains my reference worktrees that
+    are used for Claude to use as quick references (e.g. when splitting a huge
+    proof-of-concept implementation branches into smaller stacked PRs)