adds head of staff job flag (#80415)

## About The Pull Request
as we added a command role that isn't a head of staff, itd be good to
untie some checks from the command department
so i added a job flag for that, and moved what made sense to different
traits that are added to head of staff minds

## Why It's Good For The Game
revs (the gamemode not the players) shouldnt care about the bridge
assistant existing

## Changelog
🆑
fix: bridge assistant no longer passes some head of staff checks
qol: if you steal a command member's liver, you can now sabre better!
/🆑

code/controllers/subsystem/dynamic/dynamic_rulesets_latejoin.dm

@@ -128,7 +128,7 @@
 		return FALSE
 	var/head_check = 0
 	for(var/mob/player in GLOB.alive_player_list)
-		if (player.mind.assigned_role.departments_bitflags & DEPARTMENT_BITFLAG_COMMAND)
+		if (player.mind.assigned_role.job_flags & JOB_HEAD_OF_STAFF)
 			head_check++
 	return (head_check >= required_heads_of_staff)