fix(frontend): keep workspace interactive when SSR auth probe cannot reach gateway (#3493) (#3495)

* fix(frontend): keep workspace interactive when SSR auth probe cannot reach gateway (#3493)

When the SSR auth probe at /api/v1/auth/me times out or fails, the
workspace layout used to render a static fallback page without
AuthProvider or QueryClientProvider, making logout and every other
interaction non-functional until the gateway recovered.

Render the normal WorkspaceContent in 'gateway_unavailable' mode
instead, surfacing a polite offline banner that re-probes the gateway
in the background and hides itself the moment refreshUser() returns
an authenticated user. The probe is reentrancy-guarded so a slow
gateway cannot pile up parallel /auth/me requests.

Closes #3493

* fix(workspace): silent probe in offline banner to avoid /login redirect during gateway recovery (#3493)

The banner previously delegated retry probes to AuthProvider.refreshUser(),
which treats any 401 from /api/v1/auth/me as 'session expired' and
force-redirects to /login. During gateway recovery, the first few requests
may transiently return 401 before the gateway is fully ready, which would
incorrectly kick the user out — defeating the purpose of the offline banner.

Now the banner silently fetches /api/v1/auth/me itself and only delegates
to refreshUser() on 200 OK. Non-200 responses (401 / 5xx / network) are
swallowed and retried on the next interval tick, ensuring the user stays
logged in across short gateway outages.

Verified in Docker:
- docker pause deer-flow-gateway → banner appears, page interactive
- docker unpause deer-flow-gateway → banner auto-disappears within 10s,
  user remains on /workspace/chats/new with full session restored
- All 117 unit tests pass

* fix(workspace): fix banner polling leak and persistent 401 handling (#3493)
- Stop polling immediately after user recovery: add user to effect dependencies, cleanup interval when user !== null
- Handle persistent 401: trigger login redirect after 3 consecutive unauthorized responses
- Extract decision logic to pure helper, add 8 unit tests covering all critical paths

* fix(workspace): address CR feedback on gateway offline recovery (#3493)

- gateway-offline-banner-helpers: decrement (not reset) auth-failure
  streak on transient outcomes so a flapping gateway (401 alternating
  with 5xx) still converges on session-expired
- gateway-offline-banner: reuse probe response body to apply user
  directly via new AuthProvider.applyUser, halving the recovery burst
  against an already-struggling gateway
- gateway-offline-banner: extract classifyProbe into helpers for unit
  testability; log probe failures via console.warn instead of swallowing
- gateway-offline-fallback: new shared component used by both workspace
  and (auth) layouts so auth pages recover the same way the workspace
  does, fixing the lockup where bare static HTML had no AuthProvider
- AuthProvider.logout: fall back to hard navigation when the gateway
  logout fetch fails, matching legacy form-POST behaviour and avoiding
  stale client state during outage
- tests: extend gateway-offline-banner-helpers.test with flapping
  convergence and classifyProbe branch coverage (19 cases total)

frontend/src/app/(auth)/layout.tsx

@@ -1,7 +1,7 @@
-import Link from "next/link";
 import { redirect } from "next/navigation";
 import { type ReactNode } from "react";
 
+import { GatewayOfflineFallback } from "@/components/workspace/gateway-offline-fallback";
 import { AuthProvider } from "@/core/auth/AuthProvider";
 import { getServerSideUser } from "@/core/auth/server";
 import { assertNever } from "@/core/auth/types";
@@ -25,18 +25,17 @@ export default async function AuthLayout({
     case "unauthenticated":
       return <AuthProvider initialUser={null}>{children}</AuthProvider>;
     case "gateway_unavailable":
+      // Auth pages have no banner of their own, so render one here. The
+      // fallback's AuthProvider replaces the bare-HTML branch that
+      // previously locked users out without any logout/retry capability.
       return (
-        <div className="flex h-screen flex-col items-center justify-center gap-4">
-          <p className="text-muted-foreground">
-            Service temporarily unavailable.
-          </p>
-          <Link
-            href="/login"
-            className="bg-primary text-primary-foreground hover:bg-primary/90 rounded-md px-4 py-2 text-sm"
-          >
-            Retry
-          </Link>
-        </div>
+        <GatewayOfflineFallback renderBanner>
+          <div className="flex h-screen flex-col items-center justify-center gap-4">
+            <p className="text-muted-foreground">
+              Service temporarily unavailable.
+            </p>
+          </div>
+        </GatewayOfflineFallback>
       );
     case "config_error":
       throw new Error(result.message);

frontend/src/app/workspace/layout.tsx

@@ -1,6 +1,6 @@
-import Link from "next/link";
 import { redirect } from "next/navigation";
 
+import { GatewayOfflineFallback } from "@/components/workspace/gateway-offline-fallback";
 import { AuthProvider } from "@/core/auth/AuthProvider";
 import { getServerSideUser } from "@/core/auth/server";
 import { assertNever } from "@/core/auth/types";
@@ -28,31 +28,13 @@ export default async function WorkspaceLayout({
     case "unauthenticated":
       redirect("/login");
     case "gateway_unavailable":
+      // GatewayOfflineFallback supplies the AuthProvider; WorkspaceContent
+      // already mounts the banner inside its sidebar layout, so renderBanner
+      // stays false here to avoid double-mounting.
       return (
-        <div className="flex h-screen flex-col items-center justify-center gap-4">
-          <p className="text-muted-foreground">
-            Service temporarily unavailable.
-          </p>
-          <p className="text-muted-foreground text-xs">
-            The backend may be restarting. Please wait a moment and try again.
-          </p>
-          <div className="flex gap-3">
-            <Link
-              href="/workspace"
-              className="bg-primary text-primary-foreground hover:bg-primary/90 rounded-md px-4 py-2 text-sm"
-            >
-              Retry
-            </Link>
-            <form action="/api/v1/auth/logout" method="post">
-              <button
-                type="submit"
-                className="text-muted-foreground hover:bg-muted rounded-md border px-4 py-2 text-sm"
-              >
-                Logout &amp; Reset
-              </button>
-            </form>
-          </div>
-        </div>
+        <GatewayOfflineFallback>
+          <WorkspaceContent gatewayUnavailable>{children}</WorkspaceContent>
+        </GatewayOfflineFallback>
       );
     case "config_error":
       throw new Error(result.message);

frontend/src/app/workspace/workspace-content.tsx

@@ -4,6 +4,7 @@ import { Toaster } from "sonner";
 import { QueryClientProvider } from "@/components/query-client-provider";
 import { SidebarInset, SidebarProvider } from "@/components/ui/sidebar";
 import { CommandPalette } from "@/components/workspace/command-palette";
+import { GatewayOfflineBanner } from "@/components/workspace/gateway-offline-banner";
 import { WorkspaceSidebar } from "@/components/workspace/workspace-sidebar";
 
 function parseSidebarOpenCookie(
@@ -16,7 +17,11 @@ function parseSidebarOpenCookie(
 
 export async function WorkspaceContent({
   children,
-}: Readonly<{ children: React.ReactNode }>) {
+  gatewayUnavailable = false,
+}: Readonly<{
+  children: React.ReactNode;
+  gatewayUnavailable?: boolean;
+}>) {
   const cookieStore = await cookies();
   const initialSidebarOpen = parseSidebarOpenCookie(
     cookieStore.get("sidebar_state")?.value,
@@ -26,7 +31,10 @@ export async function WorkspaceContent({
     <QueryClientProvider>
       <SidebarProvider className="h-screen" defaultOpen={initialSidebarOpen}>
         <WorkspaceSidebar />
-        <SidebarInset className="min-w-0">{children}</SidebarInset>
+        <SidebarInset className="min-w-0">
+          <GatewayOfflineBanner gatewayUnavailable={gatewayUnavailable} />
+          {children}
+        </SidebarInset>
       </SidebarProvider>
       <CommandPalette />
       <Toaster position="top-center" />