[Feature]: Control group that adds new units of a type to itself

### Describe the Feature

Inspired by https://www.beyondallreason.info/commands/group-units-auto

1. Select unit(s), assign to group with hotkey A.
2. When units of the same type are constructed, they are added to the group.
3. You can remove units from the group with hotkey B.

### Expected Behavior

_No response_

### Screenshots

_No response_

### Additional context

_No response_

Start by locating the existing control-group hotkey handling, unit selection and assignment logic, and the path used when units are constructed. Trace how units are added to and removed from groups. Done means same-type constructed units join the selected group after hotkey A, while hotkey B removes units as described.

Written by the indexing model from the issue text.