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/Player/ExpandedPlayerWindowManager.swift

@@ -70,8 +70,8 @@ final class ExpandedPlayerWindowManager: NSObject {
         // Mark expanding state for mini player coordination
         appEnvironment.navigationCoordinator.isPlayerExpanding = true
 
-        // Get the current player mode for window configuration
-        let mode = appEnvironment.settingsManager.macPlayerMode
+        // Whether the window should float above other windows (always on top).
+        let floating = appEnvironment.settingsManager.macPlayerFloating
 
         // Host a lightweight two-phase root instead of ExpandedPlayerSheet directly.
         // AppKit won't composite the window to screen until the hosted SwiftUI view
@@ -133,8 +133,8 @@ final class ExpandedPlayerWindowManager: NSObject {
         // Make ExpandedPlayerWindowManager itself the delegate to avoid lifecycle issues
         window.delegate = self
 
-        // Configure window level based on mode
-        configureWindowLevel(window, floating: mode.isFloating)
+        // Configure window level based on the floating preference
+        configureWindowLevel(window, floating: floating)
 
         // Center window on screen
         window.center()

Yattee/Views/Player/macOS/MacOSPlayerControlsView.swift

@@ -113,6 +113,24 @@ struct MacOSPlayerControlsView: View {
 
             Spacer(minLength: 12)
 
+            // Floating (always-on-top) toggle — only meaningful for the separate
+            // window presentation, so hidden in the inline sheet and in fullscreen.
+            if let settings = appEnvironment?.settingsManager,
+               settings.macPlayerSeparateWindow, !isFullscreen {
+                Button {
+                    settings.macPlayerFloating.toggle()
+                } label: {
+                    Image(systemName: settings.macPlayerFloating ? "pin.fill" : "pin")
+                        .font(.system(size: 15, weight: .semibold))
+                        .foregroundStyle(.white)
+                        .frame(width: 30, height: 30)
+                        .background(.ultraThinMaterial, in: Circle())
+                }
+                .buttonStyle(.plain)
+                .help(Text("player.controls.keepOnTop"))
+                .accessibilityLabel(Text("player.controls.keepOnTop"))
+            }
+
             if onClose != nil {
                 Button {
                     onClose?()

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"),