Stress-test scoped UI activation for leaks and resource retention

## Objective

Repeatedly create, show, close, and dispose scoped Forms and nested controls. Capture retained managed objects, service scopes, event subscriptions, native handles, GDI/USER objects, and throughput. Provide baseline and fixed/proposed results with reproducible methodology.

## Completion guidance

- Keep the implementation focused on the objective while allowing the assignee to improve the approach based on research.
- Document important decisions, rejected alternatives, dependencies, and follow-up work.
- Add or update tests and documentation appropriate to the work.
- Verify locally and in CI where the task changes code or generated artifacts.

Start by defining a reproducible workload that repeatedly creates, shows, closes, and disposes scoped Forms with nested controls. Measure retained managed objects, service scopes, event subscriptions, native handles, GDI/USER objects, and throughput, then establish baseline and fixed/proposed results. Done means the methodology, decisions, dependencies, follow-up work, and appropriate tests and documentation are recorded and verification is completed.

Written by the indexing model from the issue text.