refactor(core-trpc): break the core-api package cycle

core-trpc imported AppRouter (type-only) from core-api, which depends
on the features, which depend on core-trpc — a cycle that killed every
turbo graph walk (lint/build/CI) and an illegal core -> core-composition
boundary edge. The tRPC context is now router-agnostic (AnyTRPCRouter);
useTRPC takes the router type as a generic and each feature exports a
type-only app-slice (e.g. BlogAppSlice) mirroring its mount key, so UI
hooks keep full procedure typing without touching the composition layer.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/marketing-pages/src/integrations/api/router.ts

@@ -32,3 +32,13 @@ export const marketingPagesRouter = router({
 });
 
 export type MarketingPagesRouter = typeof marketingPagesRouter;
+
+/**
+ * This feature's slice as it is mounted in the app router (the `marketingPages` key
+ * in @repo/core-api). UI hooks pass it to `useTRPC<MarketingPagesAppSlice>()` so
+ * they stay fully typed without core-trpc (or this feature's client code)
+ * depending on the composition layer. Type-only: erased at compile time.
+ */
+export type MarketingPagesAppSlice = ReturnType<
+  typeof router<{ marketingPages: typeof marketingPagesRouter }>
+>;

packages/marketing-pages/src/ui/hooks/use-page-by-slug.ts

@@ -2,10 +2,11 @@
 
 import { useSuspenseQuery } from "@tanstack/react-query";
 import { useTRPC } from "@repo/core-trpc";
+import type { MarketingPagesAppSlice } from "../../integrations/api/router";
 import type { Page } from "../../entities/models/page";
 
 export function usePageBySlug(slug: string) {
-  const trpc = useTRPC();
+  const trpc = useTRPC<MarketingPagesAppSlice>();
   // A missing slug now rejects with NOT_FOUND (PageNotFoundError), so a
   // resolved query always carries a Page.
   return useSuspenseQuery(

packages/marketing-pages/src/ui/hooks/use-site-settings.ts

@@ -2,10 +2,11 @@
 
 import { useSuspenseQuery } from "@tanstack/react-query";
 import { useTRPC } from "@repo/core-trpc";
+import type { MarketingPagesAppSlice } from "../../integrations/api/router";
 import type { SiteSettings } from "../../entities/models/site-settings";
 
 export function useSiteSettings() {
-  const trpc = useTRPC();
+  const trpc = useTRPC<MarketingPagesAppSlice>();
   return useSuspenseQuery(
     trpc.marketingPages.siteSettings.queryOptions({}),
   ) as { data: SiteSettings };