Issue-807: Fix and re-enable plugin building

[efuller]

Summary

Fixes #807

This pull request restores the plugin package to the workspace, which was previously removed to prevent build issues affecting the rest of the project. The root cause was a webpack error:

Module not found: TypeError: Cannot read properties of undefined (reading 'tap')

Key changes:

• Updates the root package.json to include the plugin directory as a workspace alongside packages/*. This ensures plugin is managed by the monorepo tooling (Yarn or npm).
• Updates the plugin/package.json build script to use npx @alleyinteractive/build-tool@latest build, ensuring the latest build tool version is used and avoiding reliance on a potentially outdated local installation.

With these changes, the plugin should build successfully, and its integration with the rest of the project is restored.

Testing

• Ensure the plugin builds successfully without triggering the webpack error.
• Verify that the rest of the project builds and runs as expected with the plugin re-enabled.

Checklist

• All tests are passing
• Code follows the project's coding standards
• Documentation is updated if necessary

[changeset-bot]

⚠️ No Changeset found

Latest commit: d16feca

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR