sketch: Introduce versions for sketch state
diff --git a/webui/src/fixtures/dummy.ts b/webui/src/fixtures/dummy.ts
index f18acf7..39148cd 100644
--- a/webui/src/fixtures/dummy.ts
+++ b/webui/src/fixtures/dummy.ts
@@ -343,6 +343,7 @@
 ];
 
 export const initialState: State = {
+  state_version: 2,
   message_count: initialMessages.length,
   total_usage: {
     start_time: "2025-04-24T10:32:00.679057+01:00",