Adding a "Agent" Selection just like "Tool" selection dialog

[cicorias]

Any thoughts on a "Agent" selection -- even for now a "prefix" for "hve" core agents vs workspace/repo based agents to make it easier to select, de-select, sort, etc. for a User?

1. a prefix of "hv:" would help determine between local/repo/workspace and the hve-core ones --
2. even better a "agent" selection dialog would be great as this list keeps growing -- and we have dropdown hell approaching :)