chore(08-01): add Drizzle migration snapshot for TypeScript-only schema change

- Create drizzle/0006_type_discriminant.sql (empty SQL - no DDL required)
- Create drizzle/meta/0006_snapshot.json (identical DDL state to 0005)
- Update drizzle/meta/_journal.json to include 0006_type_discriminant entry
- Note: db:migrate skipped (DB unavailable); migration is a no-op placeholder

teressa-copeland-homes/drizzle/meta/_journal.json

@@ -43,6 +43,13 @@
       "when": 1774027394708,
       "tag": "0005_signing_flow",
       "breakpoints": true
+    },
+    {
+      "idx": 6,
+      "version": "7",
+      "when": 1774115178000,
+      "tag": "0006_type_discriminant",
+      "breakpoints": true
     }
   ]
 }