feat(core-*): add Vitest configs + composition tests

core-api: appRouter exposes all 4 feature routers + blog procedure shape.
core-cms: payloadConfig registers all collections + globals.
core-trpc: client + provider exports verified.

Spec: §6.1, §6.6

packages/core-cms/vitest.config.ts

@@ -0,0 +1,7 @@
+import path from "node:path";
+import { mergeConfig } from "vitest/config";
+import { nodeVitestConfig } from "@repo/core-typescript/vitest.base.node";
+
+export default mergeConfig(nodeVitestConfig, {
+  resolve: { alias: { "@": path.resolve(__dirname, "./src") } },
+});