bug(mat-select-panel): select panel always animates in from top when nested inside a mat-dialog

[geertjansen]

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

20.x

Description

The mat-select-panel receives an incorrect transform-origin: top center; when it is nested within a mat-dialog causing the animation to always animate in from the top, regardless of where it is positioned from the select input field.

Reproduction

StackBlitz link: https://stackblitz.com/edit/rch3kw7b?file=src%2Fexample%2Fdialog-data-example.ts
Steps to reproduce:

1. open the dialog
2. resize the viewport such that the select-panel should appear above the mat-select
3. trigger the mat-select panel

Expected Behavior

The panel should animate in from the bottom, when it is rendered above the select input.

Actual Behavior

The panel animates in from the top.

Environment

• Angular: 21.1.0
• CDK/Material: 21.1.0
• Browser(s): Google Chrome 146.0.7680.165
• Operating System (e.g. Windows, macOS, Ubuntu): macOS