fix: html-router modals and add insta snapshot tests.

Avoid nested forms in the scratchpad editor, centralize modal lifecycle in modal.js, return HTMX partials from archive, and add template compile plus layout snapshots.

html-router/tests/snapshots/not_found_main.snap

@@ -0,0 +1,17 @@
+---
+source: html-router/tests/router_integration.rs
+expression: main
+---
+
+        
+<main class="container justify-center flex-grow flex mx-auto mt-4">
+  <div class="flex flex-col space-y-4 text-center justify-center">
+    
+  <h1 class="text-2xl font-bold  text-error">
+    404
+  </h1>
+  <p class="text-2xl my-4">Page Not Found</p>
+  <p class="text-base-content/60">The page you&#x27;re looking for doesn&#x27;t exist or was removed.</p>
+  <a href="/" class="btn btn-primary mt-8">Go Home</a>
+
+  </div>