fix(sw): guard navigator.serviceWorker access before feature check; fix EOF newline

Accessing navigator.serviceWorker.controller before the 'serviceWorker' in navigator
guard would throw a TypeError on browsers without SW support. Moved the guard into
the had_controller expression so the property is never accessed on unsupported browsers.

Also adds the missing trailing newline to core__export.ts.

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

src/routes/+layout.svelte

@@ -346,7 +346,9 @@ $effect(() => {
     // Added 2026-06-22 to close this gap.
     // Capture before registering — if null, this is first activation (fresh page load)
     // and the reload is unnecessary since assets were already fetched without the SW.
-    const had_controller = !!navigator.serviceWorker.controller;
+    // Guard must be part of the expression: navigator.serviceWorker doesn't exist on
+    // browsers without SW support, so accessing .controller before checking would throw.
+    const had_controller = 'serviceWorker' in navigator && !!navigator.serviceWorker.controller;
     const on_controller_change = () => {
         if (had_controller) window.location.reload();
     };