Playback menu seek items now follow the durations from the active player
controls preset instead of hardcoded 10s/30s labels. AppEnvironment caches
the active preset's center settings (refreshed on preset change
notifications) so menu commands can read them synchronously.
Add secondary seek durations (default 30s) to CenterSectionSettings,
configurable on macOS in Seek Durations settings, used by Shift+arrows in
the player and Cmd+Shift+arrows in the Playback menu.
Also let Cmd-based key equivalents pass through the player keyboard
monitor so menu shortcuts (e.g. Cmd+Option+arrow previous/next video)
work while the player window has focus, and unify macOS built-in preset
primary seek at 10s to match iOS/tvOS (built-in presets version 8).
Render the macOS control bar button row and top bar from the active
preset's sections via a new MacOSControlsSectionRenderer, replacing the
hardcoded QuickTime-style rows in MacOSControlBar. Add a keepOnTop
button type and macOS-specific button availability lists, and adapt the
player controls settings editors (preset editor, section editor, button
configuration) for macOS.
Also apply the preset font style to the control bar time labels, and
update the built-in macOS Default preset order (queue before transport,
fullscreen at the end), bumping builtInPresetsVersion to 7.
