Add a renderer for applications running on the primary screen. This
renderer uses relative cursor positioning, and works with all the same
primitives as the alternate screen.
Fix a bug where repositioning was never turned back to false. This was a
nasty one with huge perf implications.
Set internal cells to a space and default on init. This prevents us from
writing them. As a result, we now issue a hardware clear on resize.
Previously, stopping the read thread would not fully clean up the tty.
This could result in issues such as #9 where the terminal state was
borked upon return to shell or if temporarily exiting the TUI.
Fixes: #9
Refactor the main API to split Loop and Vaxis types. This enables the
core Vaxis type to be more easily referenced in other types, since it
doesn't require a comptime type parameter. This will make the switch to
the zg unicode library easier.