fix(auto-update-checker): defer npm registry check until first idle

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

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

src/hooks/auto-update-checker/hook/deferred-idle-check.ts

@@ -0,0 +1,4 @@
+export function scheduleDeferredIdleCheck(runCheck: () => void): void {
+  const timeout = setTimeout(runCheck, 5000)
+  timeout.unref?.()
+}