[fromageGB]

As tramticket said, forget forcing/non-forcing 2♥ : have both.

The way I play transfer advances is probably the same as anyone else, ie :
1) Bids between overcaller's suit and opener's (at the next higher level of course) are forcing.
2) Bids of opener's suit up to the one beneath overcaller's suit are transfers.
3) Raise of overcaller's suit is weak.
4) Higher bids are what you wish, and for me they are fit jumps - designed to aid competitive bidding, they are raises to the level of next higher opener's suit (not stronger) and show length in the suit bid.
4b) A fit jump can be at any higher level, where you wish to compete to that level.

A big and very important benefit is that bidding 2M of partner's suit is a weak raise, while transferring to that suit is a stronger raise. For me, I assume 12hcp for a 1♠ open, and have an unopposed reply of 2♠ = 7-10hcp when 3 cards. My assumption is that an overcall can be typically 2 hcp lighter than an open, so 10 hcp, so my "full strength" 2♥ transfer to 2♠ is correspondingly stronger, at 9-12 hcp. Therefore a direct raise here to 2♠ is up to 8 hcp only.

Indeed the transfer raise can be any strength stronger than the nominal 9-12 because it is forcing, and I can rebid should partner just bid 2♠. All 3 card raises can therefore start this way. (4 card raises 9+ start with a jump cue bid of opener's suit).

Partner is not obliged to complete the transfer to a new suit, but would if he has a hand that would pass a "weak 2" type advancer. The benefit here is that the stronger overcaller is playing the suit in the concealed hand.

Applying this to the discussed sequence of (1♣) 1♠ (pass) ?? having hearts, 2♦ is a transfer to a 5+ card heart suit, and if partner completes as he usually would, you can pass 2♥ when weak, and bid on if invitational or better - perhaps showing partial spade support. So both forcing and non-forcing hands are catered for - have your cake and eat it.

Applying this to the OP hand, (1♣) 1 ♥ (pass) 1♠ is forcing, so 2♠ is a fit jump as Cyberyeti discussed in post #10.

A thoroughly recommended method, and easy for anyone to adopt.