When the king arrives you will have both a king and a duke, the king will want better rooms than the duke he will also have an advisor with him.
Quoted for truth, though I didn't see an advisor with my monarch, just the Queen and King Consort.
By any chance did your Liaison get killed before the Queen arrived?
No, but on further examination I know what happened; apparently the advisor in question is an elf from a captured and conquered elven civ. At the next siege, he'll be murdered to death, as is only proper for an elf like him.
but I got a monarch who's actually useful; competent farmer in all fields, swordsdwarf of some skill, and quite willing to throw animals in cages for me.
It sounds like he came disguised as a peasant wich will happen if you strike a certain fun vein
That or he just switched on the labours via Dwarf Manager or something.
Nah - "All Dwarves Harvest" is probably turned on, which includes nobles; also, caging animals is one of the few things that any dwarf will do. Additionally, it's not uncommon for the King to have combat experience and actually be wielding a weapon - while you can't activate him into the military, he'll probably be happy to attack any enemies he sees.
No such cheats, and I don't mean grower; Queenie's a Great Thresher, Miller, Milker, Dyer, Butcher, Brewer, Cook, Herbalist, and Grower, Professional Tanner, Accomplished Cheese Maker, and Competent Swordsdwarf, aside from the social skills. "All dwarves harvest" is off. The King Consort, meanwhile, is a Great Siege Operator. Somehow I get the impression these monarchs were promoted from the ranks. Must remember to check the legends.