Centre the offline banner over the content column

frontend/src/components/Common/ConnectionBanner.tsx

@@ -1,7 +1,6 @@
 import { WifiOff } from "lucide-react"
 import { AnimatePresence, motion } from "motion/react"
 import { useSyncExternalStore } from "react"
-import { createPortal } from "react-dom"
 
 import { ago } from "@/components/Health/queries"
 import { connectionStore } from "@/lib/connectionStore"
@@ -17,10 +16,11 @@ import { isPortal } from "@/lib/portal"
  * stale readings with a timestamp are more use than an empty page, which is
  * why the banner leads with when we last heard anything.
  *
- * Drawn on `document.body` rather than where it is mounted. `position: fixed`
- * resolves against the nearest ancestor carrying a transform, a filter or a
- * `backdrop-filter`, and the shell floats several of those — inside them the
- * banner centres on the content column instead of the viewport.
+ * Centred over the content column rather than the window: it belongs to what
+ * is being read, not to the shell around it. That is what `sticky` inside the
+ * content column buys — no sidebar width to track and nothing to recompute
+ * when the sidebar collapses — and `h-0` keeps it out of the flow, so nothing
+ * below it moves when the banner appears.
  */
 export function ConnectionBanner() {
   const connection = useSyncExternalStore(
@@ -30,19 +30,19 @@ export function ConnectionBanner() {
   )
   if (!isPortal()) return null
 
-  return createPortal(
-    <AnimatePresence>
-      {connection.offline && (
-        <motion.div
-          variants={fadeIn}
-          initial="hidden"
-          animate="visible"
-          exit="hidden"
-          role="status"
-          aria-live="polite"
-          className="pointer-events-none fixed inset-x-0 top-4 z-50 flex justify-center px-4"
-        >
-          <div className="flex items-center gap-2 rounded-full border border-border bg-card/80 px-4 py-2 text-sm shadow-e2 backdrop-blur-md">
+  return (
+    <div className="pointer-events-none sticky top-4 z-50 flex h-0 justify-center px-4">
+      <AnimatePresence>
+        {connection.offline && (
+          <motion.div
+            variants={fadeIn}
+            initial="hidden"
+            animate="visible"
+            exit="hidden"
+            role="status"
+            aria-live="polite"
+            className="flex items-center gap-2 rounded-full border border-border bg-card/80 px-4 py-2 text-sm shadow-e2 backdrop-blur-md"
+          >
             <WifiOff className="size-4 shrink-0 text-muted-foreground" />
             <span className="font-medium">Installation offline</span>
             <span className="text-muted-foreground">
@@ -50,10 +50,9 @@ export function ConnectionBanner() {
                 ? `last seen ${ago(connection.lastSeen / 1000)} — reconnecting…`
                 : "reconnecting…"}
             </span>
-          </div>
-        </motion.div>
-      )}
-    </AnimatePresence>,
-    document.body,
+          </motion.div>
+        )}
+      </AnimatePresence>
+    </div>
   )
 }

frontend/src/routes/_layout.tsx

@@ -29,10 +29,11 @@ function Layout() {
 
   return (
     <SidebarProvider className="bg-card">
-      {/* Renders nothing unless this page is served through a portal. */}
-      <ConnectionBanner />
       <AppSidebar />
       <SidebarInset className="bg-card">
+        {/* Renders nothing unless this page is served through a portal.
+            Inside the inset so it centres over the content, not the window. */}
+        <ConnectionBanner />
         {/* The sidebar carries its own collapse control; a phone has no
             sidebar on screen to carry it. */}
         <header className="sticky top-0 z-10 flex h-16 shrink-0 items-center gap-2 px-4 md:hidden">