nix/frontend: refresh stale dist-layout comment

The output-layout block was written before:
- the dashboard's app.js → tabs.js rename (#495)
- the flow.html / flow.js page (#406 / #485)
- the SharedWorker stream-worker.js (#448)
- the build.mjs split-into-static/ subdir convention

Brings the comment in line with what `find dist -type f` actually
prints for both packages. Pure documentation refresh; install phase
and build hashes untouched.

nix/frontend.nix

@@ -14,10 +14,14 @@
 # the Rust binaries serve via `tower_http::ServeDir`:
 #
 #   $out/dashboard/   the hive-c0re dashboard SPA assets
-#       index.html app.js app.js.map dashboard.css favicon.svg
+#       index.html flow.html favicon.svg
+#       static/{tabs,flow,stream-worker}.js{,.map}
+#       static/dashboard.css
 #   $out/agent/       the per-agent default UI (layered with
 #                     hyperhive.frontend.extraFiles at activation time)
-#       index.html app.js stats.html stats.js agent.css screen.html
+#       index.html stats.html screen.html
+#       static/{app,stats}.js{,.map}
+#       static/agent.css
 #
 # The dashboard favicon lives outside the npm tree (`branding/hyperhive
 # .svg` at the repo root) — we copy it in during the install phase so