tests/ui: a failure's annotation on GitHub names the line of run.mjs

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/ui/run.mjs

@@ -989,7 +989,7 @@ for (const { name, fn } of tests) {
     failed++
     console.log(`FAIL ${name}\n     ${String(err?.stack || err).split("\n").slice(0, 6).join("\n     ")}`)
     // On GitHub Actions, also as an annotation: readable without the job's log.
-    if (process.env.GITHUB_ACTIONS) console.log(`::error title=tests/ui::${`${name}: ${String(err?.message || err)}`.replace(/%/g, "%25").replace(/\r/g, "%0D").replace(/\n/g, "%0A").slice(0, 900)}`)
+    if (process.env.GITHUB_ACTIONS) console.log(`::error title=tests/ui::${`${name}: ${String(err?.message || err)} (${String(err?.stack || "").match(/run\.mjs:\d+/)?.[0] || ""})`.replace(/%/g, "%25").replace(/\r/g, "%0D").replace(/\n/g, "%0A").slice(0, 900)}`)
   }
 }
 await browser.close()