test(hooks): remove unsafe test assertions

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/stop-continuation-guard/index.test.ts

@@ -31,14 +31,14 @@ describe("stop-continuation-guard", () => {
   })
 
   function createMockPluginInput() {
-    return {
+    return testCoerce<PluginInput>({
       client: {
         tui: {
           showToast: async () => ({}),
         },
       },
       directory: createTempDir(),
-    } as unknown as PluginInput
+    })
   }
 
   function createBackgroundTask(status: BackgroundTask["status"], id: string): BackgroundTask {