test(hashline): remove unsafe test assertions

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

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

src/__tests__/perf/plugin-init-team-mode-resume-defer.test.ts

@@ -16,11 +16,11 @@ function makeHangingClient(): {
     hangCount.value += 1
     return new Promise<never>(() => {})
   }
-  const client = {
+  const client = testCoerce<PluginInput["client"]>({
     session: {
       get: sessionGet,
     },
-  } as unknown as PluginInput["client"]
+  })
   return { hangCount, client }
 }