fix: address Cubic findings for runtime fallback child sessions

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

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

src/hooks/runtime-fallback/index.test.ts

@@ -1,5 +1,4 @@
-declare const require: (name: string) => any
-const { describe, expect, test, beforeEach, afterEach, spyOn } = require("bun:test")
+import { describe, expect, test, beforeEach, afterEach, spyOn } from "bun:test"
 import { createRuntimeFallbackHook } from "./index"
 import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
 import * as sharedModule from "../../shared"