refactor(core): Move getPackageJson utility to core package (#12224)

packages/core/src/utils/package.ts

@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  readPackageUp,
+  type PackageJson as BasePackageJson,
+} from 'read-package-up';
+
+export type PackageJson = BasePackageJson & {
+  config?: {
+    sandboxImageUri?: string;
+  };
+};
+
+export async function getPackageJson(
+  cwd: string,
+): Promise<PackageJson | undefined> {
+  const result = await readPackageUp({ cwd });
+  if (!result) {
+    // TODO: Maybe bubble this up as an error.
+    return;
+  }
+
+  return result.packageJson;
+}