Scenario: select a long note that doesn't fit on screen maximize and edit the note (in any order) ensure the note still doesn't fit on screen press pagedown

Before this commit, the cursor would no longer be visible. Any attempt to move the cursor would then crash the editor.

The cause, as expected, was a missing cache invalidation (Text.redraw_all).

I also had to move some code around so I'm not invalidating on every frame.

Still more evidence that eliminating the caching in lines2.love and its descendants was a win. But it'll likely never be a priority to port pensieve to use lines2.love..