Moving SSH Clients to macOS? Test SFTP After Reconnecting

A macOS SSH reconnect can succeed even when SFTP drag-and-drop uploads and transfer status updates are still broken.

After fixing upload handling and sidebar refresh in DartShell, reconnecting to the same host restored SFTP upload behavior.

The test flow was updated to verify SSH reconnection and SFTP uploads together, not just terminal login.

This matters for SSH client migration because a login-only check can miss file-transfer regressions.