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"

frontend/packages/agent/src/stats.js

@@ -507,15 +507,10 @@ window.Chart = Chart;
       // When accessed via hive-gateway the page lives at `/agent/<name>/`
       // on the same origin as the dashboard. Detect via path prefix
       // rather than the direct port (which is unreachable or wrong scheme
-      // behind HTTPS TLS termination). The dashboard SPA lives at
-      // `dashboard.html` — the `/` root now serves the H0M3 menu hub.
+      // behind HTTPS TLS termination). The dashboard SPA is the `/` root.
       dl.href = window.location.pathname.startsWith("/agent/")
-        ? window.location.origin + "/dashboard.html"
-        : "http://" +
-          window.location.hostname +
-          ":" +
-          s.dashboard_port +
-          "/dashboard.html";
+        ? window.location.origin + "/"
+        : "http://" + window.location.hostname + ":" + s.dashboard_port + "/";
     } catch (_) {
       /* non-fatal */
     }