Bug: Flag hotkeys (Cmd+1-7) stop working in Preview pane after switching profiles on macOS

> Launch Anki.
> Open a second profile via Profiles ► Switch Profile.
> Go to Browse.
> In the card list, select any card or note so it loads in the Preview pane on the right.
> While the focus remains inside the Preview pane, press Cmd+1 … Cmd+7 to apply a flag.
>
> Actual behaviour
>
> Nothing happens—no flag is applied while focus is in the Preview pane.

In the first load case, the browser's menu is retained when opening the preview. In subsequent cases, preview seems to be given its own menubar, so the browser shortcuts become inaccessible.

Originally reported on https://forums.ankiweb.net/t/bug-flag-hotkeys-cmd-1-7-stop-working-in-preview-pane-after-switching-profiles-on-macos/62996/7

Reproduce the issue by switching profiles, opening Browse, selecting a card, and focusing the Preview pane on macOS. Trace how the Preview pane and menubar are created across the first and subsequent profile loads. Done means Cmd+1 through Cmd+7 applies the selected flag while focus remains in the Preview pane.

Written by the indexing model from the issue text.