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-api/tsconfig.json

@@ -2,9 +2,13 @@
   "extends": "@repo/core-typescript/base.json",
   "compilerOptions": {
     "outDir": "dist",
-    "rootDir": "src",
+    "rootDir": ".",
     "declaration": false,
-    "declarationMap": false
+    "declarationMap": false,
+    "types": ["vitest/globals"],
+    "paths": {
+      "@/*": ["./src/*"]
+    }
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]