Xterm.js is what is used in Proxmox (3rd layer), but is the easiest to use and supports copy / paste via browser.
But I still do not any need for a SSH web console, when an App is available for all platforms.
An unneeded Web-Interface for a maintainence tool has all the caveats and attack vectors a web site like WordPress may have, but with the much greater risk of exposing root, not just another system user like apache or whatever…
Something for the more lazy here, who like to give themselves the illusion of being top secure with all gimicks!