fix(updates): keep the update modal's footer buttons on one line

The footer wrapped every label mid-word ("Check / now", "Copy / command")
because nothing stopped the text breaking and the modal was too narrow to
hold four buttons.

Three changes, smallest first:

  - `whitespace-nowrap` on the footer container. `white-space` inherits, so
    one class keeps every label on its own line without touching each button.
  - `flex-wrap` alongside it, so a translation that still outgrows the modal
    breaks the ROW rather than the words.
  - `max-w-lg` -> `max-w-2xl` on the dialog.

Those alone were not enough in Vietnamese: the button's restarting label is
a full sentence ("Đã build xong — đang khởi động lại bảng điều khiển...",
52 chars), which put the row over the width on its own. That sentence is
already shown in the status banner directly above the footer, so the button
now uses a new short `restartingShort` key and the banner keeps the full
one unchanged.

client/src/i18n/locales/en/updates.json

@@ -25,5 +25,6 @@
   "releaseUnavailable": "Could not read the latest release from the repository ({{reason}}); fell back to comparing commits.",
   "pluginAutoNote": "This dashboard is installed as a Claude Code plugin. \"Update now\" pulls the new plugin version, reinstalls the runtime, and restarts the server for you — it takes a few minutes. Newly added skills and slash commands only appear in an already-open Claude Code session after you run /reload-plugins there.",
   "pluginUpdating": "Pulling the new plugin version and reinstalling the runtime — this takes a few minutes, the page reloads itself when the new server is up...",
-  "lastPluginUpdateFailed": "The last plugin update failed at step \"{{step}}\": {{error}} — run /agenthub-update in Claude Code to recover."
+  "lastPluginUpdateFailed": "The last plugin update failed at step \"{{step}}\": {{error}} — run /agenthub-update in Claude Code to recover.",
+  "restartingShort": "Restarting…"
 }