Promote to UAT: GRO-2094 React bootstrap error instrumentation (#45)

Co-authored-by: The Dogfather <20+gb_dogfather@noreply.git.farh.net>
Co-committed-by: The Dogfather <20+gb_dogfather@noreply.git.farh.net>

src/main.tsx

@@ -2,9 +2,41 @@ import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
 import { BrowserRouter } from "react-router-dom";
 import { App } from "./App.js";
+import { ErrorBoundary } from "./ErrorBoundary.js";
 import { installDevFetchInterceptor } from "./lib/devFetch.js";
 import "./index.css";
 
+// --------------------------------------------------------------------
+// Global error capture (GRO-2094).
+//
+// Symptom: React root stays empty at /login — bundle parses, no console
+// errors, no error boundary fallback. Some failure is being swallowed
+// before it reaches React's commit phase. These listeners make sure any
+// thrown error or unhandled promise rejection is at least visible in
+// the console (and in the Playwright network/console log) instead of
+// vanishing into the void.
+// --------------------------------------------------------------------
+function reportGlobalError(kind: string, payload: unknown): void {
+  // eslint-disable-next-line no-console
+  console.error(`[${kind}]`, payload);
+}
+
+window.addEventListener("error", (event) => {
+  reportGlobalError("window.error", {
+    message: event.message,
+    filename: event.filename,
+    lineno: event.lineno,
+    colno: event.colno,
+    error: event.error,
+  });
+});
+
+window.addEventListener("unhandledrejection", (event) => {
+  reportGlobalError("unhandledrejection", {
+    reason: event.reason,
+  });
+});
+
 installDevFetchInterceptor();
 
 const root = document.getElementById("root");
@@ -12,8 +44,10 @@ if (!root) throw new Error("Root element not found");
 
 createRoot(root).render(
   <StrictMode>
-    <BrowserRouter>
-      <App />
-    </BrowserRouter>
+    <ErrorBoundary>
+      <BrowserRouter>
+        <App />
+      </BrowserRouter>
+    </ErrorBoundary>
   </StrictMode>
 );