feature: add sv-router, page structure and redirect to home from any other page

src/app/App.svelte

@@ -6,21 +6,22 @@
 /**
  * App Component
  *
- * Application entry point component. Wraps the main page route within the shared
+ * Application entry point component. Wraps the active route within the shared
  * layout shell. This is the root component mounted by the application.
  *
  * Structure:
  * - QueryProvider provides TanStack Query client for data fetching
  * - Layout provides sidebar, header/footer, and page container
- * - Page renders the current route content
+ * - Router renders the matched route component
  */
-import Page from '$routes/Page.svelte';
+import '$routes/router';
+import { Router } from 'sv-router';
 import { QueryProvider } from './providers';
 import Layout from './ui/Layout.svelte';
 </script>
 
 <QueryProvider>
     <Layout>
-        <Page />
+        <Router />
     </Layout>
 </QueryProvider>

src/routes/Home.svelte

@@ -1,6 +1,6 @@
 <!--
-    Component: Page
-    Description: The main page component of the application.
+    Component: Home
+    Root route — comparison workspace.
 -->
 <script lang="ts">
 import { ComparisonView } from '$widgets/ComparisonView';

src/routes/Redirect.svelte

@@ -0,0 +1,10 @@
+<!--
+    Component: Redirect
+    Mounts only when an unmatched route is hit; immediately replaces the URL
+    with the home route. Kept until additional routes exist.
+-->
+<script lang="ts">
+import { navigate } from './router';
+
+navigate('/', { replace: true });
+</script>

src/routes/index.ts

@@ -0,0 +1,7 @@
+export {
+    isActive,
+    navigate,
+    p,
+    preload,
+    route,
+} from './router';

src/routes/router.ts

@@ -0,0 +1,23 @@
+import { createRouter } from 'sv-router';
+import Home from './Home.svelte';
+import Redirect from './Redirect.svelte';
+
+/**
+ * Single-page router for glyphdiff.
+ *
+ * Currently exposes one route; structure exists so additional routes can be
+ * added without touching the app shell.
+ */
+export const {
+    isActive,
+    navigate,
+    p,
+    preload,
+    route,
+} = createRouter({
+    '/': Home,
+    /**
+     * Any unmatched path redirects to home until additional routes exist.
+     */
+    '*notfound': Redirect,
+});