Fix Qt context-menu shutdown crash

[dovvnloading]

Summary

• make the application-wide context-menu filter safe during PySide/Shiboken teardown
• remove the filter before normal Qt quit and Python interpreter shutdown
• tolerate late Qt wrapper exceptions without leaking through QObject::eventFilter
• add regression coverage for type teardown and explicit detachment

Root cause

The previous workflow run completed all 475 tests, then exited with code 1 during interpreter shutdown. PySide dispatched a final application event after the QMenu wrapper type had begun tearing down; isinstance(watched, QMenu) raised SystemError from the global event filter. The follow-up local run also exposed that leaving the filter registered could produce a native Python access violation.

Validation

• python -m compileall -q graphlink_app — passed
• python -m pytest -q --basetemp .pytest-tmp-fresh — 477 passed, exit code 0
• context-menu regression suite — 5 passed
• minimal Qt menu creation/show/close/interpreter-shutdown smoke — exit code 0
• git diff --check — passed