Add Insights tab and server-side route

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/arc-web/app/layouts/app-shell.tsx

@@ -20,6 +20,7 @@ const user = {
 const navigation = [
   { name: "Start", href: "/start" },
   { name: "Pipeline Runs", href: "/pipelines" },
+  { name: "Insights", href: "/insights" },
   { name: "Settings", href: "/settings" },
 ];
 

apps/arc-web/app/routes.ts

@@ -10,6 +10,7 @@ export default [
   layout("layouts/app-shell.tsx", [
     route("start", "routes/start.tsx"),
     route("pipelines", "routes/pipelines.tsx"),
+    route("insights", "routes/insights.tsx"),
     route("settings", "routes/settings.tsx"),
   ]),
 ] satisfies RouteConfig;

apps/arc-web/app/routes/insights.tsx

@@ -0,0 +1,9 @@
+import type { Route } from "./+types/insights";
+
+export function meta({}: Route.MetaArgs) {
+  return [{ title: "Insights — Arc" }];
+}
+
+export default function Insights() {
+  return null;
+}