bug(cdk/tree): cdkTreeNodeToggle not focusable with keyboard since v18

[jbuiquan]

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

17.x

Description

I migrated the CDK from version 17 to 18.
Since then, on a nested tree, I can't navigate with keyboard on tree item buttons with cdkTreeNodeToggle directive as tabindex=-1 has been added.
In term of accessibility, it's impossible to use the tree with keyboard.

Am i missing something ?

In the cdk documentation it can't be done either (see stackblitz forked from the documentation).

Reproduction

StackBlitz link: https://stackblitz.com/edit/yyzovrer-bnm3z1wu
Steps to reproduce:

1. Navigate with keyboard in the preview section
2. Try to focus on a tree item and toggle it with Enter or Space

Expected Behavior

I expect to be able to navigate with keyboard on the tree items and toggle with Enter or Space to expand/collapse its content.

Actual Behavior

When navigating with tab i only focus on the first element then i need to use arrow keys.
When focusing an item pressing Enter or Space doesn't do anything.

Environment

• Angular: 18.2
• CDK/Material: 18.2.14
• Browser(s): Firefox/Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Ubuntu