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>

CHANGELOG.md

@@ -16,6 +16,34 @@ for 1.0.0 have something to be assembled from.
 
 ## Unreleased
 
+## 1.8.4
+
+Two things that kept showing up after they should have gone away.
+
+- **"A new version is ready" no longer appears on a page that is already the
+  new version.** After an update the toast showed up on every page, even one just
+  fetched with Ctrl+Shift+R, and reloading never made it go away. It fired
+  whenever a new service worker was waiting. But a page loaded after the update
+  already *is* the update: pages always come from the server, and every
+  stylesheet and script they name carries the release in its address. The
+  worker that waits is nearly always the one from the previous release, still
+  holding the tab, because a reload opens the new page before the old one goes
+  away. The toast now compares the waiting worker's release with the page's
+  own, so it only appears in a tab that was opened before the update. For the
+  same reason, pressing Reload in one tab no longer reloads the other tabs that
+  are already up to date. That matters when one of them has a reply streaming
+  into it.
+
+- **Switching tabs on Administration → Prompts no longer lifts the page.**
+  Choosing any tab but the first pushed the whole window up by the height of
+  the title bar and left a blank strip along the bottom, under the sidebar too.
+  The prompt cards' hidden labels were positioned against the page instead of
+  the panel. That made the page 6,771px tall behind a window that cannot scroll
+  by hand, and the tab switch then scrolled it anyway. Every scrolling area now
+  contains what is inside it, and a tab switch moves only the panel that
+  scrolls. Administration → General on a small phone had the same leak and is
+  fixed with it.
+
 ## 1.8.3
 
 The model picker on a phone, which could not be read once a chat was open.