BTW, who on earth is declarer? With AQxxxxx xx x Axx, they had 12 aces on top: lead a
♦ at some relatively early point... and they'd be crazy to play any other way, given that a
♥ lead would probably have led to a set.
So we can assume AQxxxxx Qx x Axx, with the
♦ maybe the J....I doubt that you can safely infer that partner has specifically 86xxx of diamonds, because that leaves declarer with the singleton J9, which is an impossible holding
You didn't tell us that declarer ruffed the last
♣, so I assume she didn't.
It is difficult to be sure what to do when you don't get the
♦ suit right and don't tell us what dummy pitches to in the 4 card ending.
My guess is that she comes down to void AJ10 void x and in her hand x Qx J void, and then tables the last
♠, with you having void Kx A J.
You cannot pitch the
♦ IFF declarer has that J.. she plays it and repeats the squeeze, such that your
♥K shows up.
If you pitch the
♣, she may decide to take her 12 tricks...
♥ to the A and cash the
♣... she risks going down if you have made a nice falsecard, holding onto xx in
♥, to look like a player with Kx.
If you pitch a
♥, she really has no choice but to take the
♥ hook now... a questionable line in that she risks going down in a cold contract, but she might be trying to beat those in 6N.... an ironclad contract from her partner's side.
Well, maybe not so: if your partner has the Kx
♥ and the
♦A, he may have been reduced to Kx A and can be endplayed.... but maybe declarer is the trusting sort, who believe a defender's signals against slams

...but maybe a defender in that position would reduce to K Ax? Too many variables to worry about.
I pitch the
♣ in this assumed end position, since the alternatives lead inexorably to 13 tricks.
If she has xx in
♥s, she still comes to only the 12 tricks she started with, since the last 3 cards in dummy are void AJ void x and she can only take the
♥ and the
♣
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari