User asked: '标签使用鼠标右键应该有复制标签的功能'
In ui/terminal_tab_widget.py _on_tab_context_menu:
- Added '📋 复制标签' action between '重命名' and '关闭标签'
- New method _duplicate_tab(idx): creates a new terminal tab for
the same host (reuses SSH connection, opens independent shell
channel via paramiko invoke_shell)
- New tab title = '<src_title> (副本)' with ⚪ state dot
- If host not connected: duplicate creates a placeholder tab
- If host connected: duplicate immediately opens a new shell
Verified: 3 tabs after duplicating 'test-server' (欢迎 + ⚪ test-server
+ ⚪ test-server (副本))
All tests still pass.