feat: implement phase 5 bun_bundle bootstrap

tests/bundle_test/verify_bundle.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+bundle="$1"
+
+if [[ ! -f "${bundle}" ]]; then
+  echo "Bundle output not found: ${bundle}" >&2
+  exit 1
+fi
+
+if [[ ! -s "${bundle}" ]]; then
+  echo "Bundle output is empty: ${bundle}" >&2
+  exit 1
+fi