Move first-thread selection to the client in Conpherence
Summary: Ref T2421. For mobile, we don't want to select the first thread, since we'll just show a list of threads. Move this behavior to the client and do it when the page is shown on a desktop (or the view is changed to a desktop).
Test Plan: Viewed /conpherence/, saw first thread selected. Switched threads.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2421
Differential Revision: https://secure.phabricator.com/D5502