Re-enable paged output after a file event. - #6045

Overview

An interesting glitch from the Discord;
https://discord.com/channels/862108724948500490/1444704371295129741

User reported that after updating the scratch file the pager no longer worked;

Implementation approach and notes

Turns out an IORef was being disabled on every File Event, but was never being re-enabled.

I changed it so that whether an output is paged depends on the output message itself.

Interesting/controversial decisions

I considered a couple approaches (see commit history);

• Easiest fix is to just set the IORef back on each new message type; but global state led to this bug in the first place, doesn't seem great.
• Another option was to edit the notify of the Env before running each step
• Use paging depending on the type of message we're printing

I went with the latter approach since it seems the most semantically correct to me, and is also the most flexible.

Test coverage

Tested manually; seems tough to add an automated test for this one