swarm-ui: serve the hyperhive favicon

Same pattern frontend.nix already uses for the dashboard: the SVG
lives outside the npm tree at branding/hyperhive.svg, copied into
$out during the nix install phase (not build.mjs, so plain npm build
consumers still work, same split frontend.nix uses). Added the
matching <link rel="icon"> to index.html.

frontend/packages/swarm-ui/src/index.html

@@ -4,6 +4,7 @@
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>hyperhive swarm</title>
+  <link rel="icon" type="image/svg+xml" href="/favicon.svg">
   <link rel="stylesheet" href="static/colors.css">
   <link rel="stylesheet" href="static/theme.css">
   <link rel="stylesheet" href="static/swarm-ui.css">

nix/packages/default.nix

@@ -188,7 +188,9 @@ in
   # above, kept a separate package for the same reason: not every hive
   # runs the swarm controller, so this shouldn't ride along in
   # `packages.default`'s closure.
-  swarm-ui = pkgs.callPackage ./swarm-ui.nix { };
+  swarm-ui = pkgs.callPackage ./swarm-ui.nix {
+    branding-svg = ../../branding/hyperhive.svg;
+  };
 
   # Bundled browser assets — see ./frontend.nix. Output is
   # $out/{dashboard,agent}/ which the Rust binaries serve via

nix/packages/swarm-ui.nix

@@ -1,4 +1,4 @@
-{ buildNpmPackage }:
+{ buildNpmPackage, branding-svg }:
 
 # Static build of the swarm-level UI shell (project-bootstrap scope:
 # empty start page, no functionality yet — see
@@ -27,7 +27,9 @@
 # `npm run build --workspaces` frontend.nix runs) via an explicit
 # `npm run build --workspace=…` buildPhase, so a dashboard/agent-only
 # change doesn't need to rebuild (or re-review the output of) this
-# derivation.
+# derivation. The favicon (`branding/hyperhive.svg`, same file
+# `./frontend.nix` copies for the dashboard) is likewise copied in
+# during install — it lives outside the npm tree.
 
 buildNpmPackage {
   pname = "hyperhive-swarm-ui";
@@ -48,6 +50,7 @@ buildNpmPackage {
     runHook preInstall
     mkdir -p $out
     cp -r packages/swarm-ui/dist/. $out/
+    cp ${branding-svg} $out/favicon.svg
     runHook postInstall
   '';