Fix logout button not actually logging out the user

The auth:logout event listener in applicationBootstrap.js fires
synchronously during authService.logout(), setting __handled = true and
starting handleAuthLogout as fire-and-forget. When requestLogout() then
checked detail.__handled, it saw true and returned early — before
applyLoggedOutUiState() could update the UI.

Two changes fix this:

1. Remove the __handled early-return guard from requestLogout() so it
   always awaits handleAuthLogout.

2. Add a promise-based dedup guard to handleAuthLogout so the event
   listener's fire-and-forget call and requestLogout's awaited call
   share a single execution instead of running the logout cleanup twice.

https://claude.ai/code/session_01ArpiYU9bNdzme5xBHWnKuS

js/app/authSessionCoordinator.js

@@ -516,10 +516,6 @@ export function createAuthSessionCoordinator(deps) {
       const detail = await this.authService.logout();
 
       if (detail && typeof detail === "object") {
-        if (detail.__handled === true) {
-          return detail;
-        }
-
         try {
           detail.__handled = true;
         } catch (error) {
@@ -532,6 +528,22 @@ export function createAuthSessionCoordinator(deps) {
     },
 
     async handleAuthLogout(detail = {}) {
+      // Deduplicate concurrent calls — the auth:logout event listener may
+      // fire-and-forget this method while requestLogout() also awaits it.
+      // Return the in-flight promise so both callers resolve together.
+      if (this._pendingLogoutPromise) {
+        return this._pendingLogoutPromise;
+      }
+
+      this._pendingLogoutPromise = this._executeAuthLogout(detail);
+      try {
+        return await this._pendingLogoutPromise;
+      } finally {
+        this._pendingLogoutPromise = null;
+      }
+    },
+
+    async _executeAuthLogout(detail = {}) {
       if (detail && typeof detail === "object") {
         try {
           detail.__handled = true;