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/transport.ts

@@ -12,7 +12,7 @@ import { GatewayError, type GatewayClient } from './client';
 import * as codec from './codec';
 import { browserOffset } from './profileValidation';
 import { registerProbe, reportOffline, reportOnline } from './connection.svelte';
-import { clearMaintenance, registerMaintenanceProbe, reportMaintenance } from './maintenance.svelte';
+import { maintenanceRecovered, registerMaintenanceProbe, reportMaintenance } from './maintenance.svelte';
 import { maintenanceRetryMs } from './maintenance';
 import { backoffMs, isConnectionCode, retryable, toGatewayError } from './retry';
 
@@ -67,7 +67,9 @@ export function createTransport(baseUrl: string): GatewayClient {
         throw err;
       }
       reportOnline();
-      clearMaintenance();
+      // A read got through: if the maintenance overlay was up, the deploy window has ended —
+      // reload to pick up the (possibly incompatible) fresh client (maintenance.svelte.ts).
+      maintenanceRecovered();
       if (res.resultCode && res.resultCode !== 'ok') throw new GatewayError(res.resultCode);
       return res.payload;
     }