refactor(tests): centralize test harness boilerplate into bundle.mjs helper

tests/run-office-export-test.mjs

@@ -4,27 +4,18 @@
 // JSON, then inspects the produced ZIP contents to check that the manuscript,
 // its chapter order, and its formatting survive the native -> DOCX path.
 // Run with: node tests/run-office-export-test.mjs
-import esbuild from "esbuild";
 import fs from "fs";
 import os from "os";
 import path from "path";
-import url from "url";
 import JSZip from "jszip";
+import { bundleForTest } from "./helpers/bundle.mjs";
 
-const out = path.resolve(`tests/.tmp-folio-office-${process.pid}.mjs`);
-await esbuild.build({
-  entryPoints: [path.resolve("src/main/office-export.ts")],
-  bundle: true,
-  platform: "node",
-  format: "esm",
+const { mod, cleanupBundle } = await bundleForTest({
+  name: "folio-office",
+  entryPoints: ["src/main/office-export.ts"],
   external: ["electron"],
-  outfile: out,
-  write: true,
-  logLevel: "silent",
 });
 
-const mod = await import(url.pathToFileURL(out).href);
-
 let failures = 0;
 const check = (name, ok) => {
   console.log(`${ok ? "PASS" : "FAIL"} ${name}`);
@@ -271,7 +262,7 @@ for (const [f, bytes] of origFiles) {
 check("folio.json unchanged", fs.readFileSync(path.join(bookDir, "folio.json")).equals(origManifest));
 
 fs.rmSync(bookDir, { recursive: true, force: true });
-fs.rmSync(out, { force: true });
+cleanupBundle();
 
 if (odtSkipped) {
   console.log("NOTE ODT verification requires LibreOffice; it was skipped.");