UsnWatcher: Add Run() and RunShared() sync methods to match Rust API

FastSeekWpf/Core/UsnWatcher.cs

@@ -102,6 +102,33 @@ public class UsnWatcher : IDisposable
         return count;
     }
 
+    /// <summary>Synchronous run loop — matches Rust UsnWatcher::run()</summary>
+    public void Run()
+    {
+        byte[] buffer = new byte[65536];
+        while (!_disposed)
+        {
+            Thread.Sleep(500);
+            Poll();
+        }
+    }
+
+    /// <summary>Synchronous run with shared checkpoint updates — matches Rust UsnWatcher::run_shared()</summary>
+    public void RunShared(List<JournalCheckpoint> sharedCheckpoints)
+    {
+        byte[] buffer = new byte[65536];
+        while (!_disposed)
+        {
+            Thread.Sleep(500);
+            Poll();
+            lock (sharedCheckpoints)
+            {
+                sharedCheckpoints.RemoveAll(c => c.DriveLetter == _drive.Letter);
+                sharedCheckpoints.Add(Checkpoint());
+            }
+        }
+    }
+
     public async Task RunAsync(CancellationToken ct)
     {
         _running = true;