Improvements and fixes

Improved

• The assistant can now take any action in an app that a person can.
• Answers in an app's chat open their sources in the document viewer.
• The builder has tabs, sections and side-by-side layouts for arranging larger apps.
• Apps can be exported as a self-contained package.
• Several apps in Trash can be selected and removed together.

Fixed

• A run keeps using the version of a workflow it started with, even if the workflow is edited while it's running.
• Starting a workflow that's already running joins the run in progress instead of starting a second one.