feat(gateway): global tier provider/model defaults with catalog-backed options

src/gateway/handlers/system.ts

@@ -95,6 +95,14 @@ export interface SystemHandlerDeps {
   getNodeLocations?: (opts?: { role?: string; nodeId?: string; limit?: number }) => NodeLocationEntry[];
   /** Optional callback to retrieve registered node connection snapshots. */
   getNodes?: (opts?: { role?: string; platform?: string; limit?: number }) => NodeEntry[];
+  /** Optional callback to retrieve provider model catalogs. */
+  getModelCatalog?: (opts?: { provider?: string; forceRefresh?: boolean }) => Promise<Array<{
+    provider: string;
+    models: string[];
+    source: 'api' | 'config' | 'unavailable';
+    error?: string;
+    fetchedAt: number;
+  }>>;
 }
 
 export function createSystemHandlers(deps: SystemHandlerDeps) {
@@ -265,5 +273,17 @@ export function createSystemHandlers(deps: SystemHandlerDeps) {
       }
       return makeResponse(request.id, { requests: deps.getActiveRequests() });
     },
+
+    'system.modelCatalog': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      if (!deps.getModelCatalog) {
+        return makeResponse(request.id, { providers: [] });
+      }
+      const params = request.params as { provider?: string; forceRefresh?: boolean } | undefined;
+      const providers = await deps.getModelCatalog({
+        provider: params?.provider,
+        forceRefresh: params?.forceRefresh === true,
+      });
+      return makeResponse(request.id, { providers });
+    },
   };
 }