hive-gateway: serve the swagger-ui theme via nginx alias, not a c0re build hook

nix/packages/default.nix

@@ -158,6 +158,11 @@ in
   xdg-icons = pkgs.callPackage ./hive-xdg-icons.nix {
     hyperhiveSvg = ../../branding/hyperhive.svg;
   };
+  # Swagger UI re-theme static override files — see
+  # ./swagger-ui-theme.nix. The gateway `alias`es these straight from
+  # the store; a theme tweak is a gateway config change, not a
+  # hive-c0re rebuild.
+  swagger-ui-theme = pkgs.callPackage ./swagger-ui-theme.nix { };
 
   # Pre-built per-container system closures. Exposed as packages
   # so operators can `nix build .#agent-base-toplevel` (or wire

nix/packages/swagger-ui-theme.nix

@@ -0,0 +1,49 @@
+{
+  stdenv,
+}:
+
+# The hand-authored Swagger UI re-theme files (`hive-c0re/swagger-ui-
+# theme/`), shipped as a standalone derivation so the gateway can
+# `alias` them straight from the nix store instead of hive-c0re's own
+# build serving them — see nix/host-modules/hive-gateway/vhosts.nix's
+# `swaggerThemeLocations`. This is what lets a CSS tweak ship as a
+# gateway config change (activate the gateway container) rather than a
+# hive-c0re rebuild+restart: the two files nginx exact-matches
+# (`/api/docs/` and `/api/docs/hyperhive-theme.css`) come from here;
+# every other Swagger UI asset (bundle.js, openapi.json, favicons, …)
+# still falls through the existing `/api/` prefix proxy to hive-c0re's
+# own vendored (unthemed) `utoipa-swagger-ui` embed, unchanged.
+#
+# Pure data: copied verbatim, no build step.
+#
+# Output layout:
+#   $out/index.html            — themed index.html Swagger UI page
+#   $out/hyperhive-theme.css   — the re-theme, consumes --baseNN vars
+#                                 from the dashboard's own colors.css
+#                                 (loaded via an absolute /static/
+#                                 colors.css <link>, same origin)
+
+stdenv.mkDerivation {
+  pname = "hyperhive-swagger-ui-theme";
+  version = "0.1.0";
+  # Narrow src keeps this derivation's input hash decoupled from the
+  # rest of the tree — a theme tweak only re-hashes this.
+  src = ../../hive-c0re/swagger-ui-theme;
+
+  dontBuild = true;
+  dontConfigure = true;
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out
+    cp -r ./* $out/
+    runHook postInstall
+  '';
+
+  dontFixup = true;
+
+  meta = {
+    description = "hyperhive Swagger UI Catppuccin Mocha re-theme (static override files)";
+    homepage = "https://forge.darkest.space/hyperhive/hyperhive";
+  };
+}