feat: add independent CLI launches and preserve shared video bookmarks

Checks/playback-progress.swift

@@ -20,7 +20,9 @@ struct PlaybackProgressChecks {
         try FileManager.default.createSymbolicLink(at: alias, withDestinationURL: file)
         let youtube = URL(string: "https://www.youtube.com/watch?v=jNQXAC9IVRw")!
 
-        var progress = PlaybackProgress(defaults: defaults)
+        let progress = PlaybackProgress(defaults: defaults)
+        let independent = PlaybackProgress(defaults: UserDefaults(suiteName: suite)!)
+        let independentFile = directory.appendingPathComponent("independent.mp4")
         progress.save(123.25, for: file)
         progress.save(18, for: otherFile)
         progress.save(9.5, for: youtube)
@@ -29,12 +31,20 @@ struct PlaybackProgressChecks {
         require(reopened.position(for: alias) == 123.25, "symlink and original file share progress")
         require(reopened.position(for: otherFile) == 18, "local files keep separate positions")
         require(reopened.position(for: youtube) == 9.5, "canonical YouTube URL persists independently of local files")
+        independent.save(27, for: independentFile)
+        let shared = PlaybackProgress(defaults: defaults)
+        require(shared.position(for: file) == 123.25 && shared.position(for: youtube) == 9.5,
+                "an independently initialized player cannot overwrite another video's bookmarks")
+        require(shared.position(for: independentFile) == 27,
+                "independent player progress is also retained")
 
         progress.save(nil, for: alias)
         let completed = PlaybackProgress(defaults: defaults)
         require(completed.position(for: file) == nil, "completion clears progress through either file identity")
         require(completed.position(for: otherFile) == 18 && completed.position(for: youtube) == 9.5,
                 "clearing one video preserves other videos")
+        require(completed.position(for: independentFile) == 27,
+                "clearing progress in one player preserves a different player's bookmark")
         for position in [Double.nan, Double.infinity, -Double.infinity, -1, 0] {
             progress.save(position, for: file)
             require(PlaybackProgress(defaults: defaults).position(for: file) == nil,
@@ -44,6 +54,15 @@ struct PlaybackProgressChecks {
         defer { isolated.removePersistentDomain(forName: suite + ".isolated") }
         require(PlaybackProgress(defaults: isolated).position(for: youtube) == nil,
                 "injected preference domains remain isolated")
+        isolated.set([file.standardizedFileURL.absoluteString: 42.5, youtube.absoluteString: 15],
+                     forKey: "playbackPositions")
+        let migrated = PlaybackProgress(defaults: isolated)
+        require(migrated.position(for: alias) == 42.5 && migrated.position(for: youtube) == 15,
+                "existing local and YouTube bookmarks survive the shared-history migration")
+        migrated.save(43, for: file)
+        let migratedAgain = PlaybackProgress(defaults: isolated)
+        require(migratedAgain.position(for: file) == 43 && migratedAgain.position(for: youtube) == 15,
+                "opening another player preserves both migrated bookmarks and newer progress")
         print("Playback progress checks passed")
     }
 }