[Feature Request] Package selector for adding an action

If it makes sense, it could be an enhancement to the CLI if it detects multiple packages in the yaml, and asks in which package to add the runtime action.

Start by locating the CLI command that adds a runtime action and the YAML parsing path for projects with multiple packages. Determine how package selection should be presented and validated; done means the command identifies multiple packages and lets the user choose where to add the action.

Written by the indexing model from the issue text.