Fix model fallback across main/background/sync agents

src/plugin/system-transform.ts

@@ -0,0 +1,12 @@
+import type { CreatedHooks } from "../create-hooks"
+
+export function createSystemTransformHandler(args: {
+  hooks: CreatedHooks
+}): (input: { sessionID: string }, output: { system: string[] }) => Promise<void> {
+  return async (input, output): Promise<void> => {
+    await args.hooks.beastModeSystem?.["experimental.chat.system.transform"]?.(
+      input,
+      output,
+    )
+  }
+}