feat(ui): reload the SPA on maintenance recovery

The deploy that ends a maintenance window may ship a client-incompatible change
(wire/schema bump), and the in-session bundle is the old one. On recovery, reload to
pick up the fresh client instead of just hiding the overlay. Ordering is safe: the edge
maintenance flag (deploy/prod-deploy.sh) spans the WHOLE roll and clears only at script
exit — after the gateway (which serves the embedded SPA) has rolled — so the edge 503s
everything until the entire deploy is live; recovery therefore always serves the new SPA.
A window.__maint.recover() hook + e2e cover the reload.

ui/src/lib/gateway.ts

@@ -6,7 +6,7 @@ import type { GatewayClient } from './client';
 import { MockGateway } from './mock/client';
 import { createTransport } from './transport';
 import { reportOffline, reportOnline } from './connection.svelte';
-import { clearMaintenance, reportMaintenance } from './maintenance.svelte';
+import { clearMaintenance, maintenanceRecovered, reportMaintenance } from './maintenance.svelte';
 
 const isMock = import.meta.env.MODE === 'mock';
 
@@ -23,9 +23,12 @@ if (isMock && typeof window !== 'undefined') {
   };
   // The mock never produces a real 503, so the e2e drives the maintenance overlay directly
   // (the store's poll is inert in mock — no probe is registered — so `off` clears it).
-  (window as unknown as { __maint?: { on(retryAfterMs?: number): void; off(): void } }).__maint = {
+  (
+    window as unknown as { __maint?: { on(retryAfterMs?: number): void; off(): void; recover(): void } }
+  ).__maint = {
     on: (retryAfterMs = 15000) => reportMaintenance(retryAfterMs),
     off: clearMaintenance,
+    recover: maintenanceRecovered,
   };
   // Drive the auto-match opponent join deterministically from the e2e (the mock otherwise
   // attaches a robot on a timer).