fix: add --parallel to pnpm dev so all packages start concurrently

Without --parallel, tsc --watch in core blocks studio from starting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -22,7 +22,7 @@
   },
   "scripts": {
     "build": "pnpm -r build",
-    "dev": "pnpm -r dev",
+    "dev": "pnpm -r --parallel dev",
     "test": "pnpm -r test",
     "lint": "pnpm -r lint",
     "typecheck": "pnpm -r typecheck",