SPIKE: In the LMS app, how do we best handle when a web page reloads, keeping the client embedded but losing the LMS context?

Copying from this private issue: https://github.com/hypothesis/support/issues/195

## Feature Request Form
### Problem you are trying to address with this feature
Web pages sometimes reload almost immediately after being loaded in Via. This causes our client to remain embedded, but we lose the LMS context, meaning LMS users **think** they're still seeing an LMS group but actually end up creating web app accounts and annotating there.

A bug where this is illustrated: https://github.com/hypothesis/support/issues/189 (including a Canvas link to replicate the issue).
A proposed solution to this issue: https://github.com/hypothesis/support/issues/193

We've also seen this issue when instructors use http:// protocols in assignment URLs and sites are set up to automatically forward to https://.

### Your solution
No proposed solution; the goal for this spike is to investigate why the client remains embedded and use that to propose a solution to the problem for URL assignments in the LMS app.