[BUG] Inconsistent "Alternative mouse setup" between CCG and ZH

[tintinhamans]

The behavior of alternative mouse setup is different between CCG and ZH, I think the ZH implementation is superior.

See this example where it's hard to deselect units in CCG:

2025-03-03T13-50-59.webm

I believe that left clicking should deselect a unit like it does in ZH.