I merged from master and did my best to fix the conflicts but I'm seeing the activation not happen when cmd+clicking (tested on mac). See the activate logs in the gif below, the first one worked but the other 3 didn't:

The reason was because _currentLink was undefined here:

https://github.com/xtermjs/xterm.js/blob/e2ac4b45d0747ae3d6ab3eb1e3ba9be7cbdec351/src/browser/Linkifier2.ts#L129

I also notice the link seems to get disposed when you click it, or just the rendering part of it anyway. We definitely want to keep the underline when clicked.