[Feature] Add "compact" as executable task

I use some /project commands, and i would really like it to be able to be explicitly say "compact after each task"

Or, since the /compact command supports what to focus on, i would really like it to be able to have in my prompt "when compacting, focus on ...". So we have a bit more control when compacting happens, and it doesnt wait for the last possible second to do it.

By the way, sometimes its too late for compacting, as it exceeds the limit.