brand: unclip sidebar wordmark, styled dark 404, human files error, Element brand text

From the brand review: the sidebar truncated 'Tactical Media Broadcast Hub'
on eleven desktop routes; unknown routes rendered a stock white Next.js 404;
solo users saw the raw 'groupid must be a UUID' validation text on Files;
Element's config brand string still read 'OccupyMedia Hub'.

apps/web/src/app/(main)/files/page.tsx

@@ -133,7 +133,10 @@ export default function FilesPage(): React.ReactElement {
           return;
         }
         setSource("live");
-        setError(errorMessage(err));
+        const message = errorMessage(err);
+        // Solo accounts have no collective yet: the API's validation text leaks
+        // an implementation detail, so give the human next step instead.
+        setError(/groupid/i.test(message) ? "Files live inside a collective — create or join one, then its library appears here." : message);
       })
       .finally(() => {
         if (!controller.signal.aborted) setLoading(false);

apps/web/src/app/not-found.tsx

@@ -0,0 +1,19 @@
+import Link from "next/link";
+
+export default function NotFound(): React.ReactElement {
+  return (
+    <div className="flex min-h-full flex-col items-center justify-center gap-4 bg-bg p-6 text-center">
+      <p className="text-5xl font-semibold tracking-tight text-accent">404</p>
+      <h1 className="text-lg font-semibold">This page was silenced. Our stories aren&apos;t.</h1>
+      <p className="max-w-sm text-xs text-text-faint">
+        Nothing lives at this address — but the newsroom does.
+      </p>
+      <Link
+        href="/streams"
+        className="rounded-md bg-accent px-4 py-2 text-xs font-semibold text-white transition-opacity hover:opacity-90"
+      >
+        Back to the newsroom
+      </Link>
+    </div>
+  );
+}

apps/web/src/components/shell/sidebar.tsx

@@ -42,7 +42,7 @@ export function Sidebar(): React.ReactElement {
       <div className="flex items-center gap-2.5 border-b border-border-subtle px-4 py-4">
         <LogoMark size={30} title="Tactical Media Broadcast Hub" />
         <div className="min-w-0">
-          <div className="truncate text-sm font-semibold tracking-tight">Tactical Media Broadcast Hub</div>
+          <div className="text-xs font-semibold leading-tight tracking-tight">Tactical Media Broadcast Hub</div>
           <div className="truncate text-2xs text-text-faint" title={workspaceName}>
             {workspaceName} ▾
           </div>