Change the Jenkins jobs so that deployment to beta happens as follows: Deploy to beta, trigger browser tests, repeat. Make it so that both do not overlap so that the tests don't run while beta is changed. (Maybe scap3 can trigger the browser tests in a way so that it would also work in production, when deploying to group0 and can roll back when they fail.)
After T130045: use a deployment branch for beta is done, push the commit in wmf/beta-try that was used in the current test run to wmf/beta-pass.
For this to work well it might require that browsertests are versioned with deployment branches, so that a browsertest run against a wiki is using the version of the test intended for the version of the code running on that wiki.