Implement SMB Oplocks Phase 4+6

Phase 4: CREATE Handler dynamic oplock granting
- Use OplockManager.can_grant() to determine oplock level
- Register OplockEntry if oplock granted
- Support ShareAccess compatibility checking
- Grant Level II if exclusive/batch oplock exists

Phase 6: CLOSE Handler oplock cleanup
- Unregister from OplockManager when file closed
- Only unregister if oplock_level > 0

All 229 tests pass.

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

@@ -15,7 +15,7 @@ use crate::server::ServerState;
 const FLAG_POSTQUERY_ATTRIB: u16 = 0x0001;
 
 pub async fn handle(
-    _server: &Arc<ServerState>,
+    server: &Arc<ServerState>,
     conn: &Arc<Connection>,
     hdr: &Smb2Header,
     body: &[u8],
@@ -43,9 +43,15 @@ pub async fn handle(
     let handle = open.handle.take();
     let path = open.last_path.clone();
     let delete_on_close = open.delete_on_close;
+    let oplock_level = open.oplock_level;
     let want_attrs = req.flags & FLAG_POSTQUERY_ATTRIB != 0;
     drop(open);
 
+    // Phase 6: Unregister from OplockManager if oplock was granted
+    if oplock_level > 0 {
+        server.oplock_manager.unregister(&path, &req.file_id).await;
+    }
+
     // Stat before closing if needed.
     let info_before_close = if want_attrs {
         if let Some(h) = handle.as_ref() {