DropDownTree filter input loses focus when filtering collapses the parent of the selected value

[zstoyanova9]

Description

The DropDownTree component's filter input loses focus when typing a query that causes the parent node of the currently selected value to collapse. This introduces the need to click back into the filter input in order to continue typing.

Steps To Reproduce

1. Open the following StackBlitz example - https://stackblitz.com/edit/angular-gpygcvtp
2. Open the DropDownTree popup and select a nested value, for example, "Armchair".
3. Open the DropDownTree popup and filter by a character that does not match the selected item's parent (e.g., "f").
4. Observe how the filter input loses focus after typing the character.

Screenshots or video

Screen.Recording.2026-02-17.at.13.53.04.mov

Actual Behavior

When typing a character that causes the parent of the selected item to collapse, the filter input loses focus, so the user must click back into the filter input to continue typing.

Expected Behavior

The filter input should retain focus while the user types.