fix(web): verify current GUI updates end to end

apps/web/tests/support/listen-probe.mjs

@@ -0,0 +1,9 @@
+import { appendFileSync } from 'node:fs'
+import { Server } from 'node:net'
+
+const marker = process.env.DSH_LISTEN_PROBE_MARKER
+const listen = Server.prototype.listen
+Server.prototype.listen = function (...args) {
+  if (marker !== undefined) appendFileSync(marker, 'listen\n')
+  return listen.apply(this, args)
+}