How crooked interior walls should one accept

[mr_bygg]

HUS AMA is applicable only if this is what you have agreed upon?!
What kind of agreement have you made?

Regardless of the agreement, one can expect the work to be performed professionally. In training material from construction educators I received from our consumer advisor when we had some issues with our build, it discusses what the term professional actually means. As I understand from the training material, AMA is often a good benchmark for what constitutes good professional work. A clip from the material titled "Professional according to the government" states

What professionalism means is not easy to specify. Prop 1984/85:110 described professionalism as "something that can be demanded of a normally skilled and knowledgeable as well as seriously working professional within the area that the given service concerns." Guidance for this can, according to the same proposition, be derived from "general or specific descriptions or instructions regarding materials and methods, etc., as well as good professional or industry practice." Manufacturers' material instructions should also, according to 1989/90:77, be included. AMA, general material and work description are often considered to set a standard for what good professionalism is.

So even if you haven't agreed that the walls should be straight and not lean, you can rely on AMA, which is often considered a good standard for what is acceptable and professional.