* feat(desktop): use shared Python backend in native macOS app

* fix(desktop): make Python lint configuration independent of runner defaults

* fix(desktop): preserve package signatures and ship dependency notices

* test(desktop): verify real credentials only in disposable CI keychains

* fix(desktop): pin interpreter archive and retain exact NuGet runtime notices

* fix(desktop): include Windows Desktop runtime third-party notices

* docs(desktop): describe Python migration and unsigned upgrade limits in release notes

* fix(ci): match backend Python selection to the deployed runtime

* fix(desktop): preserve Unicode notices on Windows

* fix(desktop): preserve notice checksums across Windows checkouts