Disable live previews on mobile
Summary:
Fixes T1895. Now that we have on-demand prviews, we can use them on mobile. On mobile:
- don't show live previews;
- only save drafts every 10 seconds.
Also, show fewer remarkup buttons on mobile to try to make sure the more important ones (preview, e.g.) fit.
Test Plan:
- Made window narrower and wider to trigger preview/no-preview behavior.
- Used DarkConsole to verify request rate.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T1895
Differential Revision: https://secure.phabricator.com/D14856