fix: add zod to apps/demo devDependencies for Vercel deployment

@objectstack/spec depends on zod at runtime. After patch-symlinks.cjs
dereferences pnpm symlinks for Vercel bundling, zod must be present as
an explicit dependency in apps/demo/node_modules/.

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>
Agent-Logs-Url: https://github.com/objectstack-ai/objectql/sessions/e3b65dd9-3cb4-4a2e-88fa-2100507f9646

Author: Copilot

CHANGELOG.md

@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- **`apps/demo`** — added explicit `@objectstack/spec` devDependency. The Vercel serverless function failed at runtime with `ERR_MODULE_NOT_FOUND` because `@objectstack/core` could not resolve its transitive `@objectstack/spec` dependency after pnpm symlinks were dereferenced by `patch-symlinks.cjs`. Adding the explicit dependency ensures the package is present at the top level of `node_modules/` for Vercel bundling.
+- **`apps/demo`** — added explicit `@objectstack/spec` and `zod` devDependencies. The Vercel serverless function failed at runtime with `ERR_MODULE_NOT_FOUND` because transitive dependencies could not be resolved after pnpm symlinks were dereferenced by `patch-symlinks.cjs`. Adding them as explicit dependencies ensures they are present at the top level of `node_modules/` for Vercel bundling.
 - **`@objectql/types`** — moved `@objectstack/spec` and `zod` from `devDependencies` to `dependencies`. The compiled JS output contains runtime imports of `@objectstack/spec` (via `z.infer<typeof Data.X>` patterns), so they must be declared as production dependencies.
 
 ### Added

apps/demo/package.json

@@ -36,7 +36,8 @@
     "@objectstack/studio": "^3.2.8",
     "@types/node": "^20.19.37",
     "hono": "^4.12.8",
-    "typescript": "^5.9.3"
+    "typescript": "^5.9.3",
+    "zod": "^4.3.6"
   },
   "engines": {
     "node": ">=20"