dashboard: serve the dashboard at /, fold kept state in as a tab, add a pages menu

Drop the H0M3 tile hub and the core page. The dashboard is now the index;
kept state is its fifth tab. A pages menu in the chrome links flow, stats,
API docs and the swarm UI. The swarm apex URL comes from
services.hyperhive.swarm.domain via HIVE_SWARM_PUBLIC_URL and the new
swarm_public_url field of the state snapshot.

frontend/packages/agent/src/components/MetaNav.tsx

@@ -31,7 +31,7 @@ export interface MetaNavProps {
   links: AgentLink[];
   forgePublicUrl: string | null;
   /** Absolute base URL of the host dashboard (`resolveDashboardBase`)
-   * — the `🧭 dashboard` item links to `${dashboardBase}dashboard.html`. */
+   * — the `🧭 dashboard` item links to `${dashboardBase}`. */
   dashboardBase: string;
 }
 
@@ -86,7 +86,7 @@ export function MetaNav({
         <div class="meta-nav-popover" role="menu" aria-label="agent links">
           <a
             class="meta-nav-item"
-            href={`${dashboardBase}dashboard.html`}
+            href={dashboardBase}
             target="_blank"
             rel="noopener"
             role="menuitem"