Fix: Remove leaked child change listener in HotgraphicModel (fixes #372)

[oliverfoster]

fixes #372

Fix

• Replaced child.on('change', ...) with this.listenTo(child, 'change', ...) in HotgraphicModel.setUpItems() so the listener is tracked against the component model and automatically removed via stopListening() when the model is torn down, instead of leaking on the child item indefinitely.

Testing

1. Add a Hot Graphic component with tooltips enabled.
2. Trigger setUpItems() multiple times for the same items (e.g. switch language / reset course).
3. Confirm only one change listener is attached per item (no growth in event listener count on the child model).
4. Confirm tooltip content still updates correctly when the item's attributes change (position, visited state, classes).

[Copilot]

Pull request overview

Fixes the listener leak described in #372 by switching tooltip-sync item listeners from being attached directly to child models to being tracked by the parent HotgraphicModel, so they can be cleaned up via stopListening() when the component model is torn down.

Changes:

• Replace child.on('change', ...) with this.listenTo(child, 'change', ...) inside HotgraphicModel.setUpItems() to ensure listener cleanup on teardown.

Suppressed comments (1)

js/hotgraphicModel.js:41

• listenTo ensures cleanup on model teardown, but setUpItems() can run multiple times on the same HotgraphicModel instance. As written, each call will add another change listener (now tracked on this), so the child’s change listener count can still grow during the model’s lifetime. Consider de-duping by storing the per-child handler and stopListening(child, 'change', prevHandler) before binding a new one.

      this.listenTo(child, 'change', () => {
        tooltipModel.set({
          ...child.toJSON(),
          ...tooltip,
          _classes: tooltipModel.get('_classes')

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[github-actions]

🎉 This PR is included in version 6.21.1 🎉

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