move swaggerUiTheme nix option out of c0re's namespace

services.hyperhive.c0re.swaggerUiTheme -> services.hyperhive.gateway.swaggerUiTheme.
hive-c0re has no relationship to this option (it's consumed entirely
by the gateway's nginx config) since the previous two commits moved
the theme files out of hive-c0re/ and gateway to hosting the whole
dist itself — the option shouldn't live in c0re's namespace either.

Pure option move: default wiring in flake.nix now sets
services.hyperhive.gateway.swaggerUiTheme instead of the c0re one;
hive-gateway/default.nix reads it via the module's own already-bound
cfg (services.hyperhive.gateway) instead of reaching into c0re's.

Verified: nix build .#swagger-ui-theme unaffected (same store path,
pure option-plumbing change, no content change); a full nixosSystem
eval of nixosModules.default resolves the option at its new path and
confirms the gateway's /api/docs/ location still aliases the correct
store path.

flake.nix

@@ -128,7 +128,6 @@
                 frontend = lib.mkDefault self.packages.${pkgs.stdenv.hostPlatform.system}.frontend;
                 assets = lib.mkDefault self.packages.${pkgs.stdenv.hostPlatform.system}.assets;
                 xdgIcons = lib.mkDefault self.packages.${pkgs.stdenv.hostPlatform.system}.xdg-icons;
-                swaggerUiTheme = lib.mkDefault self.packages.${pkgs.stdenv.hostPlatform.system}.swagger-ui-theme;
                 hyperhiveFlake = lib.mkDefault "${sources.hyperhiveFlakeSource}";
                 # Narrow docs/ source, threaded as its own meta-flake input
                 # so doc edits don't re-hash the whole flake source.
@@ -143,6 +142,9 @@
                 agentBaseToplevel = lib.mkDefault self.packages.x86_64-linux.agent-base-toplevel;
                 managerToplevel = lib.mkDefault self.packages.x86_64-linux.ruth-toplevel;
               };
+              services.hyperhive.gateway.swaggerUiTheme =
+                lib.mkDefault
+                  self.packages.${pkgs.stdenv.hostPlatform.system}.swagger-ui-theme;
             };
           hive-ci = ./nix/host-modules/hive-ci.nix;
           hive-forge = ./nix/host-modules/hive-forge;

nix/host-modules/hive-c0re/options.nix

@@ -65,19 +65,6 @@
         processes to their icon.
       '';
     };
-    swaggerUiTheme = lib.mkOption {
-      type = lib.types.package;
-      defaultText = lib.literalExpression "hyperhive.packages.\${system}.swagger-ui-theme";
-      description = ''
-        Full Swagger UI static dist, hyperhive-themed (see
-        `nix/packages/swagger-ui-theme.nix`, built on
-        `nix/packages/swagger-ui-dist.nix`). hive-gateway serves this
-        whole tree directly at `/api/docs/` — hive-c0re hosts none of
-        it, only the dynamic `/api/openapi.json` route. Override to
-        ship a custom theme (or the plain vendored dist) without a
-        hive-c0re rebuild.
-      '';
-    };
     hyperhiveFlake = lib.mkOption {
       type = lib.types.str;
       defaultText = lib.literalMD "the hyperhive flake's own filtered source store path";

nix/host-modules/hive-gateway/default.nix

@@ -27,8 +27,9 @@ let
   # Full hyperhive-themed Swagger UI dist — nginx serves this whole
   # tree straight from the store at /api/docs/, no hive-c0re fallback
   # (see vhosts.nix's `swaggerUiLocations` and
-  # nix/packages/swagger-ui-{dist,theme}.nix).
+  # nix/packages/swagger-ui-{dist,theme}.nix). Own option under this
-  swaggerUiTheme = config.services.hyperhive.c0re.swaggerUiTheme;
+  # module (not c0re's) — hive-c0re has no relationship to it.
+  swaggerUiTheme = cfg.swaggerUiTheme;
 
   # Self-signed TLS is the implicit floor: when neither an operator cert
   # (`tls.certDir`) nor ACME (`tls.acme.enable`) is configured, the gateway

nix/host-modules/hive-gateway/options.nix

@@ -254,6 +254,21 @@ in
       };
     };
 
+    swaggerUiTheme = lib.mkOption {
+      type = lib.types.package;
+      defaultText = lib.literalExpression "hyperhive.packages.\${system}.swagger-ui-theme";
+      description = ''
+        Full Swagger UI static dist, hyperhive-themed (see
+        `nix/packages/swagger-ui-theme.nix`, built on
+        `nix/packages/swagger-ui-dist.nix`). The gateway serves this
+        whole tree directly at `/api/docs/` — hive-c0re hosts none of
+        it, only the dynamic `/api/openapi.json` route (proxied
+        through, unaffected by this option). Override to ship a
+        custom theme (or the plain vendored dist) without a gateway
+        rebuild.
+      '';
+    };
+
     hsts = {
       enable = lib.mkOption {
         type = lib.types.bool;