fix(sw): skip controllerchange reload on first activation

The reload should only fire when an existing SW is replaced by a new one
(old → new), not when the SW activates for the first time on a fresh page
load (null → first). The spurious reload on fresh loads was caused by
checking unconditionally.

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

src/routes/+layout.svelte

@@ -344,7 +344,12 @@ $effect(() => {
     // silently runs whatever JS it had at the time the SW changed. This caused IDAA and
     // other users to run stale code for weeks at a time across multiple deployments.
     // Added 2026-06-22 to close this gap.
-    const on_controller_change = () => window.location.reload();
+    // 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;
+    const on_controller_change = () => {
+        if (had_controller) window.location.reload();
+    };
     if ('serviceWorker' in navigator) {
         navigator.serviceWorker.addEventListener('controllerchange', on_controller_change);
     }