fix(router): correct parseHash slice indices for detail routes

parts.slice(0,3) was returning the full path as base; should be slice(0,2)
so '#/templates/abc123' yields base='#/templates', param='abc123'.

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

web/static/js/router.js

@@ -34,7 +34,7 @@ function parseHash(hash) {
   const clean = hash || '#/templates';
   const parts = clean.split('/');
   if (parts.length >= 3) {
-    return { base: parts.slice(0, 3).join('/'), param: parts[3] || null };
+    return { base: parts.slice(0, 2).join('/'), param: parts.slice(2).join('/') };
   }
   return { base: clean, param: null };
 }