Fix setScore() ignoring item scores when _hasItemScoring is enabled

[joe-replin]

Subject of the issue/enhancement/features

When _hasItemScoring: true is set on an MCQ, setScore() always stores 0 or _questionWeight based on correctness, ignoring the selected item's _score value. A get score() getter exists that sums active item scores correctly, but setScore() was never updated to use it. Plugins that read model.get('_score') directly — including SCORM tracking and custom scoring extensions — receive the wrong value.

Your environment

• adapt-contrib-core v6.73.0
• All modern browsers
• All operating systems

Steps to reproduce

1. Create an MCQ with _hasItemScoring: true and _selectable: 1
2. Give items fractional _score values, e.g. 0, 0.25, 0.75, 1.0
3. Mark one item _shouldBeSelected: true
4. Submit the question by selecting a different item — one with _shouldBeSelected: false and _score: 0.25
5. After submission, run in the browser console:

   Adapt.components.findWhere({ _id: 'your-component-id' }).get('_score')

Expected behaviour

model.get('_score') returns 0.25 — the selected item's _score value.

Actual behaviour

model.get('_score') returns 0. setScore() treats the question as incorrect and stores 0, regardless of the selected item's _score.

Suggested Fix (if known)

Replace setScore() in ItemsQuestionModel with:

setScore() {
  this.set('_score', this.score);
}

The existing get score() getter already handles _hasItemScoring correctly. setScore() should sync the stored attribute to it rather than recalculate independently.