Do non-archery abilities that don't specify melee affect archery?
I'm not 100% sure but skills (active and passive) which don't mention a weapontype should work for every weapon.
There is a thread on gamefaq where the OP asks for critical damage vs. armor penetatrion vs flanking damage "Assuming playing an archer and using sneak attack". Nobody in this thread says something about "Archer with the Sneak Attack Passive wont work" or something like that.
And another thread where someone says
As long as something doesn't say that its for one weapon or another then it works on everything.
There is nothing to be found about this on Dragon Age Wikia.