Document compare-bloat.sh in README and AGENTS.md

Author: teknogeek0

pgcopydb-helpers/README.md

@@ -195,7 +195,20 @@ When `check-cdc-status.sh` reports **"CDC IS CAUGHT UP"** (apply backlog < 100 M
 
 6. **Switch** your application to the PlanetScale target.
 
-### 5. Clean Up
+### 5. Post-Migration (Optional)
+
+These steps are optional and can be run after the migration is complete and traffic has been switched.
+
+**Compare bloat reduction** between source and target to see how much space was reclaimed by the fresh copy. This breaks down heap, TOAST, and index sizes per table and reports overall reduction:
+
+```bash
+~/compare-bloat.sh                    # tables > 100 MB (default)
+~/compare-bloat.sh --min-size-mb 500  # only tables > 500 MB
+```
+
+The script uses catalog queries only — no table scans, no writes, no locks — and is safe to run against production databases.
+
+### 6. Clean Up
 
 After the migration is complete (or abandoned), clean up replication artifacts: