Implement SMB Oplocks Phase 3+5

Phase 3: NotificationQueue
- Add notification_tx to Connection struct
- Modify writer.rs to use tokio::select! for response + notification
- Add write_to_bytes() to OplockBreakNotification
- Support server→client async messages

Phase 5: WRITE Handler oplock break
- Get path/share_access before write
- Trigger OplockManager.break_oplock()
- Send OPLOCK_BREAK_NOTIFICATION to affected clients
- Encode and send via notification channel

All 229 tests pass.

vendor/smb-server/src/handlers/write.rs

@@ -13,7 +13,7 @@ use crate::ntstatus;
 use crate::server::ServerState;
 
 pub async fn handle(
-    _server: &Arc<ServerState>,
+    server: &Arc<ServerState>,
     conn: &Arc<Connection>,
     hdr: &Smb2Header,
     body: &[u8],
@@ -41,6 +41,34 @@ pub async fn handle(
         Some(o) => o,
         None => return HandlerResponse::err(ntstatus::STATUS_FILE_CLOSED),
     };
+    
+    // Phase 5: Get path and trigger oplock break before write
+    let (path, share_access) = {
+        let open = open_arc.read().await;
+        (open.last_path.clone(), open.share_access)
+    };
+    
+    // Trigger oplock break for conflicting clients
+    let notifications = server.oplock_manager.break_oplock(
+        &path,
+        share_access,
+        granted,
+    ).await;
+    
+    // Send notifications to affected clients
+    for notification in notifications {
+        // Build SMB2 frame for notification
+        use crate::proto::framing::encode_frame;
+        let notification_bytes = notification.write_to_bytes();
+        let mut frame = Vec::with_capacity(notification_bytes.len() + 4);
+        encode_frame(&notification_bytes, &mut frame);
+        
+        // Send via notification channel (if available)
+        if let Some(tx) = conn.notification_tx.read().await.as_ref() {
+            let _ = tx.send(frame).await;
+        }
+    }
+    
     let result = {
         let open = open_arc.read().await;
         match open.handle.as_ref() {