Add integration tests for router state based logic

We need to be able to run browser based integration tests to fully test navigation state logic (e.g., jump to source history).

Start by locating the router state and navigation logic, including the jump-to-source history path, and then find any existing browser-based integration test setup. Done means adding integration coverage that exercises these navigation state transitions and can be run in a browser.

Written by the indexing model from the issue text.