Verify core is available

Some commands require a valid core/group to be defined first. Do checks for this before proceeding. This occurred when a command was run from a different directory and an empty config.json was used.

Trace the command entry points that use the configured core/group, then reproduce the issue by running a command from a different directory with an empty config.json. Verify how missing or invalid configuration is handled before command execution; done means affected commands stop with a clear validation result instead of proceeding.

Written by the indexing model from the issue text.