[web] Keep an ID of a thick thread in the URL

Summary:
When a user opens a URL to a thick thread, we shouldn't inform the keyserver about it and ignore the id it sends us.

https://linear.app/comm/issue/ENG-9099/opening-a-link-to-a-thick-thread-resets-the-navigation-on-web

Test Plan: Refresh a web page where a thick thread is open and make sure the URL doesn't change.

Reviewers: kamil, inka

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13202