Test flake due to async route modules

[david-crespo]

Lots of test flake, but interestingly it didn’t really kick off until near the end of the conversion, so hopefully it’s due to something specific.

It only seems to happen in one browser per run, every time. And it affects different tests every time too. I don't get it.

Firefox: https://github.com/oxidecomputer/console/actions/runs/13598150882/job/38019429785
Safari: https://github.com/oxidecomputer/console/actions/runs/13635164967/job/38112041124?pr=2724
Firefox: https://github.com/oxidecomputer/console/actions/runs/13597704894/job/38018130878
Chrome: https://github.com/oxidecomputer/console/actions/runs/13609558382/job/38045006012?pr=2720

Ok finally had two browsers fail in one run: https://github.com/oxidecomputer/console/actions/runs/13635221035

[david-crespo]

#2729 seems to improve things a lot. Will close if it improves things to a tolerable degree.