A reload offer only for a page that is older, and a tab switch that moves one scroller

The update toast fired whenever a service worker was waiting, so after every
release it appeared on pages that were already the release -- including one
fetched with Ctrl+Shift+R. It now compares the waiting worker's release with
the page's own, and so does the reload that follows another tab accepting it.

On Admin -> Prompts, visually hidden labels were positioned against the page
and made the document 6771px tall behind an overflow-hidden root; the tab
handler's scrollIntoView then scrolled that root and lifted the shell 56px.
Every scroll region is now a containing block, and the handler moves only the
container that scrolls.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lembas/web/templates/base.html

@@ -152,6 +152,9 @@
   what `app.js` turns into a sentence on the settings page.
 #}
 <script>
+  /* The release this page was rendered by, for `app.js` to hold a waiting
+     worker up against -- see "A release that arrived while you were reading". */
+  window.lembasRelease = {{ version | tojson }};
   window.lembasWorker = { state: "unsupported" };
   if (!window.isSecureContext) {
     /* Reported separately from an outright failure: the fix is different. */