swarm-ui: run sw.js through nix fmt

The response.ok fix from the earlier review round was never reformatted
after editing. nix flake check has no --keep-going, so this one real
treefmt-check failure was aborting the whole check run -- and whatever
other derivation happened to be mid-build in the same parallel batch got
killed and logged with an empty error message, misread as an
infrastructure flake across many CI attempts. No logic change.

frontend/packages/swarm-ui/src/sw.js

@@ -106,7 +106,9 @@ self.addEventListener("fetch", (event) => {
         // asset on the next offline/failed fetch.
         if (response.ok) {
           const copy = response.clone();
-          caches.open(CACHE_NAME).then((cache) => cache.put(event.request, copy));
+          caches
+            .open(CACHE_NAME)
+            .then((cache) => cache.put(event.request, copy));
         }
         return response;
       })