Assuming no such agreements, I think I would rebid 2NT over 1♠. This hand seems fairly notrumpy to me, and that sequence maximizes my chances of finding a major suit fit (I cannot miss a nine card heart fit or an eight-card spade fit, whereas any other sequence seems to have a strong possibility of missing one of those two and/or playing in a 6-1 heart fit on this lousy suit).
I don't really mind 3♥, as I think a lot of people obsess too much about suit quality in that sequence, but here it has the additional problem of missing what could be a good spade fit. Bidding 2♥ or 2♠ seems like a big underbid to me, and 2♣ "natural" is not very appealing.
In fact I like 3♥ over 1NT, as partner will often (okay not always) deliver a doubleton heart on hands with less than four spades.

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