build: Exclude test files from TypeScript compilation

- Add exclusion for .test.ts and .spec.ts files in core tsconfig
- Allows tests to exist in source without blocking compilation

apps/x/packages/core/tsconfig.json

@@ -9,5 +9,9 @@
     },
     "include": [
         "src"
+    ],
+    "exclude": [
+        "src/**/*.test.ts",
+        "src/**/*.spec.ts"
     ]
 }