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/blog/src/integrations/api/router.ts

@@ -43,3 +43,13 @@ export const blogRouter = router({
 });
 
 export type BlogRouter = typeof blogRouter;
+
+/**
+ * This feature's slice as it is mounted in the app router (the `blog` key
+ * in @repo/core-api). UI hooks pass it to `useTRPC<BlogAppSlice>()` 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 BlogAppSlice = ReturnType<
+  typeof router<{ blog: typeof blogRouter }>
+>;

packages/blog/src/ui/hooks/use-article-by-slug.ts

@@ -2,10 +2,11 @@
 
 import { useSuspenseQuery } from "@tanstack/react-query";
 import { useTRPC } from "@repo/core-trpc";
+import type { BlogAppSlice } from "../../integrations/api/router";
 import type { Article } from "../../entities/models/article";
 
 export function useArticleBySlug(slug: string) {
-  const trpc = useTRPC();
+  const trpc = useTRPC<BlogAppSlice>();
   return useSuspenseQuery(trpc.blog.articleBySlug.queryOptions({ slug })) as {
     data: Article | null;
   };

packages/blog/src/ui/hooks/use-article-list.ts

@@ -2,13 +2,14 @@
 
 import { useSuspenseQuery } from "@tanstack/react-query";
 import { useTRPC } from "@repo/core-trpc";
+import type { BlogAppSlice } from "../../integrations/api/router";
 import type { Article } from "../../entities/models/article";
 
 export function useArticleList(options?: {
   status?: "draft" | "published";
   limit?: number;
 }) {
-  const trpc = useTRPC();
+  const trpc = useTRPC<BlogAppSlice>();
   return useSuspenseQuery(
     trpc.blog.listArticles.queryOptions({
       status: options?.status ?? "published",