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/Views/Settings/PlaybackSettingsView.swift

@@ -250,14 +250,10 @@ private struct BehaviorSection: View {
 
         SettingsFormSection("settings.playback.behavior.header", footer: footer) {
             #if os(macOS)
-            PlatformMenuPicker(
-                String(localized: "settings.playback.macOS.playerMode"),
-                selection: $settings.macPlayerMode
-            ) {
-                ForEach(MacPlayerMode.allCases, id: \.self) { mode in
-                    Text(mode.displayName).tag(mode)
-                }
-            }
+            Toggle(
+                String(localized: "settings.playback.macOS.separateWindow"),
+                isOn: $settings.macPlayerSeparateWindow
+            )
 
             Toggle(
                 String(localized: "settings.playback.macOS.autoResizePlayer"),