feat(core-shared): add requireEnv helper

packages/core-shared/src/lib/env.ts

@@ -0,0 +1,7 @@
+export function requireEnv(name: string): string {
+  const value = process.env[name];
+  if (!value) {
+    throw new Error(`Missing required env var: ${name}`);
+  }
+  return value;
+}