feat: terminal tabs - several machines at once, up to four terminals split in a tab by drag and drop, resizable, renamable; the top bar keeps its status in sight

internal/server/web/static/app.css

@@ -25,6 +25,11 @@ header.topbar {
   padding: 14px 24px; border-bottom: 1px solid var(--border); background: var(--panel);
 }
 header.topbar .brand { font-weight: 600; }
+/* A long machine name gives way: the links and the status stay in sight. */
+@media (min-width: 641px) {
+  header.topbar .brand { flex: 1 1 auto; min-width: 0; margin-right: 16px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+  header.topbar nav { flex: none; white-space: nowrap; }
+}
 header.topbar nav a { margin-left: 18px; color: var(--muted); }
 header.topbar nav a:hover { color: var(--text); }
 .wrap { max-width: 960px; margin: 0 auto; padding: 24px 16px; }