Unify and Simplify CLI Command Architecture

### Issue description

Handling of CLI commands is currently spread across multiple libraries, using different mechanisms for command registration.
This makes the architecture difficult to understand, maintain, and extend.
The goal is to align these approaches and introduce a clearer, more consistent command architecture.

Related: #15286

Start by reviewing the CLI command implementations across the libraries and the related issue #15286, since no specific files or entry points are named here. Map how commands are currently registered, then define a consistent architecture and verify that the involved commands still register and execute correctly.

Written by the indexing model from the issue text.