Close the last three UI leftovers: shared staff HTML, cookie domain, stock Swagger label.

verae-staff-ui holds one review template for CS and access-staff.
Staff cookies take STAFF_COOKIE_DOMAIN for a reverse-proxy host.
/docs stays vendor Swagger with an integrator banner only.

packages/zappier-customer-service/src/staff-page.js

@@ -0,0 +1,16 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import { pathToFileURL } from 'node:url';
+
+export async function staffPageHtml(opts, fallbackPath) {
+  const sibling = path.join(path.dirname(fallbackPath), '..', '..', 'verae-staff-ui', 'src', 'load.js');
+  try {
+    if (fs.existsSync(sibling)) {
+      const { loadReviewHtml } = await import(pathToFileURL(sibling).href);
+      return loadReviewHtml(opts, fallbackPath);
+    }
+  } catch {
+    /* standalone clone */
+  }
+  return fs.readFileSync(fallbackPath, 'utf8');
+}