swarm-ui: minimal agent creation page

Adds /agents: a name field that POSTs to swarm-controller's
POST /api/agents (from the CreateIdentity work), shows the queued
job node id, and links to /jobs to watch it settle. Scope matches
the issue exactly - no forge/deploy options, those aren't wired
server-side yet.

frontend/packages/swarm-ui/src/App.tsx

@@ -2,6 +2,7 @@
 // page component under `./pages/`; this file just maps paths to them.
 import { Route, Switch } from 'wouter-preact';
 import { Shell } from './shell/Shell.js';
+import { AgentsPage } from './pages/AgentsPage.js';
 import { ComponentsPage } from './pages/ComponentsPage.js';
 import { JobsPage } from './pages/JobsPage.js';
 import { OverviewPage } from './pages/OverviewPage.js';
@@ -20,6 +21,7 @@ export function App() {
     <Shell>
       <Switch>
         <Route path="/" component={OverviewPage} />
+        <Route path="/agents" component={AgentsPage} />
         <Route path="/jobs" component={JobsPage} />
         <Route path="/components" component={ComponentsPage} />
         <Route component={NotFound} />