bug(drag-drop): cdkDropListSortPredicate doesn't work if dragging item enter from top

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

`cdkDropListSortPredicate` doesn't work in certain senarios

### Reproduction

StackBlitz link: https://stackblitz.com/edit/z6ffpx7e-wg8uidxw?file=src%2Fexample%2Fcdk-drag-drop-connected-sorting-group-example.html
Steps to reproduce:
1. Open StackBlitz reproduction link
2. The code has `cdkDropListSortPredicate` applied to "Done" dropzone, the intention is preventing item being dragged to the first index
3. Drag item from "To do" zone and enter "Done" zone from top


### Expected Behavior

Item cannot be dragged & dropped to the first index in "Done"

### Actual Behavior

Item can be dragged & dropped to the first index in "Done"

### Environment

- Angular: 19.0.0
- CDK/Material: 19.0.0
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Windows

Commencez par la reproduction StackBlitz liée et examinez le comportement de cdkDropListSortPredicate lorsqu’un élément entre dans la dropzone Done par le haut. Reproduisez le cas dans Angular 19.0.0, puis vérifiez que le predicate empêche l’élément d’être déposé au premier index tout en préservant le reste du comportement de tri.

Rédigé par le modèle d'indexation à partir du texte de l'issue.