bug(cdk/tree): "insertNode" doesn't assign index property in the template's context object #31578

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

In the implementation of the insertNode method, a context object is created for the tree node template. However, not all properties are filled in. One important property is missing: index.

Reproduction

StackBlitz link:
Steps to reproduce:
1.
2.

Expected Behavior

Assign value of the method's index parameter to the context object.

Actual Behavior

Index property in template's context object is missing.

Environment

• Angular: 19.2, 20
• CDK/Material: 19, 20
• Browser(s): Goggle, Edge
• Operating System (e.g. Windows, macOS, Ubuntu): Windows