TreeSelect: overlay position is not aligned above container when virtual scrolling is used

[puschie286]

Describe the bug

the tree-select overlay position is not aligned correctly above the container when virtual scrolling is used and not enough space is available under the container element

Virtual scroll example in documentation

(this works just fine for multi-select)

Pull Request Link

No response

Reason for not contributing a PR

• Lack of time
• Unsure how to implement the fix/feature
• Difficulty understanding the codebase
• Other

Other Reason

No response

Reproducer

https://primeng.org/treeselect#virtual-scroll-doc

Environment

Documentation of primeng

Angular version

21.2.6

PrimeNG version

v21

Node version

No response

Browser(s)

Firefox 150

Steps to reproduce the behavior

1. Got to documentation and scroll to virtual scroll example
2. Scroll to a position where the overlay would be cut-off by the browser bottom
3. Open the tree select overlay
   -> see overlay being cut-off by browser bottom

Expected behavior

Overlay should be positioned above the container element