I don't seem to get click /drag/release events; not sure if it's something I did or just something textual doesn't support.

Research this: https://github.com/textualize/textual/blob/main/FAQ.md#how-can-i-select-and-copy-text-in-a-textual-app
I think this would allow system operations, like copy to clipboard, but idk if I get the events I need to update the harlequin cursor and anchor selection for text insertion.

Also research how the scroll bar implements this, since it clearly supports click+drag.