Option to freeze / not follow new requests

First off: thanks for a fabulous tool! I love it.

I have some pages that make a lot of ajax requests, some on a repeating interval. Sometimes I want to inspect one of those requests in DebugBar Companion (are we calling it DBC?) but if a new request arrives it will automatically switch. I've love a toggle button that allows me to turn off the "switch to latest request" behavior and instead freeze on the selected request.

The issue names no files, tests, or entry points. Start by tracing how incoming requests select the displayed request and where the companion UI controls that behavior; done means a toggle can freeze the selected request while later requests arrive, with normal switching restored when unfrozen.

Written by the indexing model from the issue text.