Fix macOS opening player window instead of switching video in PiP

The PiP-active guard that skips expanding the player when opening a new
video was compiled iOS-only, so on macOS a browser deep link always
re-showed the hidden player window instead of playing the new video in
the existing PiP window. Extend the guard in both openVideo overloads
and the Handoff path to macOS.

Yattee/Services/Player/PlayerService.swift

@@ -940,7 +940,7 @@ final class PlayerService {
     func openVideo(_ video: Video, startTime: TimeInterval? = nil) {
 
         // Check if MPV PiP is active - if so, don't expand the player
-        #if os(iOS)
+        #if os(iOS) || os(macOS)
         let mpvPiPActive = (currentBackend as? MPVBackend)?.isPiPActive ?? false
         #else
         let mpvPiPActive = false
@@ -993,7 +993,7 @@ final class PlayerService {
     ///   - captions: Optional array of external captions (e.g., from WebDAV subtitle files)
     func openVideo(_ video: Video, stream: Stream, audioStream: Stream? = nil, download: Download? = nil, captions: [Caption] = []) {
         // Check if MPV PiP is active - if so, don't expand the player
-        #if os(iOS)
+        #if os(iOS) || os(macOS)
         let mpvPiPActive = (currentBackend as? MPVBackend)?.isPiPActive ?? false
         #else
         let mpvPiPActive = false

Yattee/YatteeApp.swift

@@ -761,7 +761,7 @@ struct YatteeApp: App {
             // Always expand player after handoff (unless PiP is active)
             // We add a small delay to ensure ContentView has set up its .onChange observers
             // (during app launch via Handoff, the trigger can fire before the view is ready)
-            #if os(iOS)
+            #if os(iOS) || os(macOS)
             let isPiPActive = appEnvironment.playerService.state.pipState == .active
             #else
             let isPiPActive = false