I attached two pictures of an addition reaction of H-Cl to an isolated diene. Although unstated, we are meant to assume 1 equivalent of H-Cl. One picture is the answer key, and the other picture shows my work on it.
I think answer given in the official key requires some sketchy logic. I think the trisubstituted endocyclic alkene will react MUCH faster because it is able to form a tertiary benzylic carbocation in the rate limiting step. Therefore, I do not expect the monosubstituted alkene will react at all. After all, the molecule cannot "see the future" and know it will rearrange after the initial addition of the proton to the exocyclic alkene.
And even if the reaction is heated enough to make it equilibrate and allow the monosubstituted alkene to react instead, wouldn't the major product be the conjugated alkene? Resonance is not the same thing as a 1,2 shift. The nucleophile doesn't automatically attack the more stable resonance structure. I think the the monosubstituted alkene would be reacting under some severe thermodynamic control, leading to the more stable alkene as the final product, the conjugated one.