If Orion is open, and the use either does a system shutdown, or a reboot, when the shutdown routine gets to Orion, oriion says "Are you sure you want to quit Orion?" and blocks the user shkutdown. Eventually the system reports that Orion is preventing shutdown. (see figure with two modal windows.)
Typcial use case is that user does a shutdown when leaving office, maybe to update software, and leaves the computer. Next morning it is still hung partway through shutdown. 
Much better solution, used with many other apps, is to issue the same message, but if no user response after several minutes, go ahead and quit Orion so system can procede. (It's not like this is a word processor lacking autosave, user is unlikely (but possible) to lose work.) Orion will restore open tabs, anyway.
OS 15.3 (24D60), Orion Version 0.99.130.3.1-rc (WebKit 621.1.2.111.4)
Sequoia (15)
