bug(cdkDrag): Items in DropLIst Jump Down When Using DragBoundary or ConstrainPosition with Custom Preview

### 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

Items with a custom preview inside of a drop list that should be constrained either by constrainPosition or a dragBoundary appear to jump down for one frame when being dragged before constraint is applied.

### Reproduction

StackBlitz link: https://stackblitz.com/edit/stackblitz-starters-eyxb1gn5?file=src%2Fmain.ts

### Expected Behavior

Constraints are applied to drag preview on starting frame of drag.

### Actual Behavior

Constraints are not applied to drag preview until the second frame of the dragging.

### Environment

- Angular: 19.0.6
- CDK/Material: 19.1.2
- Browser(s): Chrome/Firefox
- Operating System (e.g. Windows, macOS, Ubuntu): Windows

Inizia con la riproduzione StackBlitz collegata e il relativo punto di ingresso src/main.ts, quindi riproduci il comportamento di trascinamento con un’anteprima personalizzata e dragBoundary oppure constrainPosition in Chrome o Firefox. Il lavoro è completato quando il vincolo dell’anteprima di trascinamento viene applicato nel frame iniziale, senza un salto verso il basso di un frame.

Scritto dal modello di indicizzazione a partire dal testo della issue.