Add test projects for Next.js App Router + RSC boundaries.

[kotAPI]

• Audit reference: Action item build(deps-dev): bump @babel/preset-react from 7.22.15 to 7.23.3 #112.
• Problem: Add test projects for Next.js App Router + RSC boundaries. is currently not completed, and it blocks feature parity and/or quality improvements identified in the audit.
• Scope: Implement the change with associated test coverage and documentation updates where applicable.
• Acceptance criteria:
  1. The implementation is merged with appropriate tests.
  2. Storybook/docs are updated for behavior/API changes.
  3. Release notes/changeset entry is added when user-facing behavior changes.