fix(server,desktop): browser tools report why a page failed to load#18588

@@ -187,6 +192,10 @@ export const make = Effect.gen(function* () {
     emit({ type: "attached", ...key });
   };
 
+  const loadFailed: DesktopBrowserHost["Service"]["loadFailed"] = (key, failure) => {
+    if (tabs.has(keyOf(key))) emit({ type: "loadFailed", ...key, ...failure });

@@ -1312,6 +1316,19 @@ const make = Effect.gen(function* () {
     );
   };
 
+  /**
+   * Why the tab shows the browser's error page. A desktop tab's first load can
+   * fail before this server connects, so the desktop's own report fills in.
+   */
+  const loadErrorOf = async (tab: ServerTab) => {
+    if (!tab.page.url().startsWith("chrome-error://")) return undefined;
+    if (tab.loadError !== undefined || !tab.desktop) return tab.loadError ?? undefined;
+    const reported = await Effect.runPromise(
+      desktopChannel.loadFailure({ threadId: tab.threadId, tabId: tab.tabId }),