fix: restore the production gate after the migration tasks

- rebuild editors/vscode bundles, stale since the parser escape fix
- attach the caught ParseError as `cause` in both migration validators
- drop two unused test bindings flagged by eslint

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/dev-server/test/server-fn-rpc-request-context.test.ts

@@ -9,7 +9,7 @@ import { withServerFnRequestContext } from "../src/index.ts";
 // request context, not `undefined`.
 test("a handler invoked through the server-function RPC path can read the request context", async () => {
   let seen: unknown;
-  const innerHandler = async (request: Request): Promise<Response> => {
+  const innerHandler = async (_request: Request): Promise<Response> => {
     seen = getRequestContext();
     return new Response("ok");
   };