Update demo site to use Yarn 4.x

To make development easier with the adapter (which is on yarn 4.9.4 with workspaces), we should upgrade the demo site to use yarn 4.9.4 as well

The demo site is likely in a subdirectory like 'demo' or 'examples'. Check for a package.json to see its current yarn version. Update the yarn version to 4.9.4, ensuring compatibility with workspaces. Verify the upgrade by running yarn install and testing the demo site locally.

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