Thanks for the comments. I was south and suggested that partner's hand was worth a game force (and even if you think it's not, the ability to get your shape out probably makes it right). I was interested in how the auction would go over 1S (if anyone took that route) because that's what happened at the table, but abstaining since you'd never be in that position is reasonable.
There is a funny story with this auction that I'll share (but has no bearing on the issues at hand). The full auction was (north is a beginner, so I'm certainly not suggesting this is an A/E auction

)
1H - 1S
3H - 4D [4D: North - diamonds. South -cuebid for hearts]
4S - 4N [4S: North - spades. South - cuebid for hearts; 4N: North - RKC
♠, South - RKC
♥. And East asked me what 4N was. Knowing that NS were possibly not on the same page, I wrote down my answer on a spare cc and passed it to East. This gives UI to north, but probably less than if I'd blurted out what I thought. Comments on this?]
5D - 6S [0/3 keys; to play]
6N - Pass
I bid 6N for a couple of reasons. Mostly it looks to me like if we have 12 tricks in spades, we have 12 in NT, and I felt a little better playing a potentially hopeless contract than leaving that task to my partner (except then I noticed the 4N card on the table -- drats!). My partner fumes a bit about the 6N call and passes.
In any case, the funny part of the story is that lefty puts the club ace on the table, and RHO yells something-or-other about it being his lead, so I call the director. My partner then accepts the club lead out of spite and tables his hand as dummy and lets me play it -- a very "well, you got us here" decision. Of course, opps cash 5 clubs off the top, when forbidding a club lead from the other side actually lets the contract roll on a spade guess.
"I think maybe so and so was caught cheating but maybe I don't have the names right". Sure, and I think maybe your mother .... Oh yeah, that was someone else maybe. -- kenberg
"...we live off being battle-scarred veterans who manage to hate our opponents slightly more than we hate each other. -- Hamman, re: Wolff