refactor: remove core-trpc from main (scaffoldable via gen core-package trpc)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-trpc/src/query-client.ts

@@ -1,22 +0,0 @@
-import { QueryClient } from "@tanstack/react-query";
-
-let clientQueryClient: QueryClient | undefined;
-
-const defaultOptions = {
-  queries: {
-    staleTime: 30 * 1000,
-    refetchOnWindowFocus: false,
-  },
-};
-
-export function getQueryClient(): QueryClient {
-  if (typeof window === "undefined") {
-    // Server: always create a new instance per request
-    return new QueryClient({ defaultOptions });
-  }
-  // Browser: singleton
-  if (!clientQueryClient) {
-    clientQueryClient = new QueryClient({ defaultOptions });
-  }
-  return clientQueryClient;
-}