Add `glsp repo` command for workspace and repository management

[tortmayr]

Introduce a glsp repo command for managing the multi-repository GLSP workspace.

This picks up the idea of the repo management script originally introduced in the Playwright integration and evolves it into a proper CLI command. The command should support two main use cases:

• CI / one-off operations: Individual clone, switch, and setup commands that can be composed in scripts and CI pipelines
• Local development workflows: Help contributors clone, checkout, and maintain the full set of GLSP repositories, including linking packages for local cross-repo development