Introduce PlatformMenuPicker that wraps short-option pickers in
LabeledContent + .pickerStyle(.menu) on tvOS so they render as a
compact dropdown instead of pushing a full-screen option list. On
iOS/macOS it falls through to a plain Picker, leaving rendering
unchanged.
Applied across Playback, Subtitles, Sidebar, Privacy, and Advanced
settings. Long language lists in PlaybackSettingsView are left as
push-style.
The tvOS Main Navigation list relied on .onMove with native Toggle
rows inside editMode, which leaves only the drag handle focusable on
tvOS. Replace it with a TVSidebarMainItemRow modeled on the home
customization screen: explicit up/down chevrons on the left and a
tap-to-toggle checkmark button as the row body. Required items render
disabled with a dimmed checkmark.