[Bug] Right click option `Select All` only copy contents shown in viewable screen, not all selection.

Hi!
When I type `vim /etc/ssh/sshd_config` and select all contents, then right click, click `Select All` option, only lines shown in viewable screen are copied, not the whole selection.

Similarly, in the `Outline` panel, when I choose the command `vim /etc/ssh/sshd_config`, then right click, click `Copy Output` option, only viewable contents are copied.

**Version**: WindTerm 2.6.0 Pre-release 1

No source files or tests are named. Reproduce the issue in WindTerm 2.6.0 Pre-release 1 using a long vim output, then compare terminal Select All with Outline Copy Output; done means both actions copy the complete selection or output rather than only visible lines.

Written by the indexing model from the issue text.