Split macOS player mode into window toggle + floating control

Replace the three-way macOS Player Mode picker (Separate Window /
Floating Window / Inline) with a single 'Play in a separate window'
toggle in Playback settings, and move the always-on-top choice to a
pin button in the player's top bar (window mode only).

Floating was really a transient window property (NSWindow.level), not
a peer of the window/inline structural choice — so it belongs on a live
control, not in Settings. The pin state persists across sessions.

- Replace MacPlayerMode enum with macPlayerSeparateWindow /
  macPlayerFloating bool settings
- Branch runtime presentation and window level off the two bools
- Add pin.fill/pin toggle to MacOSPlayerControlsView top bar
- Update localization; drop obsolete playerMode strings and enum tests

Yattee/Core/SettingsManager.swift

@@ -72,7 +72,8 @@ final class SettingsManager {
     var _preferPortraitBrowsing: Bool?
     #endif
     #if os(macOS)
-    var _macPlayerMode: MacPlayerMode?
+    var _macPlayerSeparateWindow: Bool?
+    var _macPlayerFloating: Bool?
     var _playerSheetAutoResize: Bool?
     #endif
 
@@ -456,7 +457,8 @@ final class SettingsManager {
         _syncSearchHistory = nil
         _searchHistoryLimit = nil
         #if os(macOS)
-        _macPlayerMode = nil
+        _macPlayerSeparateWindow = nil
+        _macPlayerFloating = nil
         _playerSheetAutoResize = nil
         #endif
         // miniPlayerShowVideo and miniPlayerVideoTapAction moved to preset