The constant context changes, mental overload, inability to focus on one thing and do it well is exactly what every software developer has been fighting against for the past thirty years because it leads to shit quality and burns you out. You're automating the burnout. Idling is a necessity, not an illness.
Your feature branch is to put things aside and send them to CI, or wait and think on them. Not to have four of them running in parallel in your head frying you.
> The constant context changes, (...)
After you put together a plan, today's models can take well over a minute to execute it. Also, your work shifts to code review and executing acceptance tests, followed by either tweaking your current change or moving on to the next change.
This is really not about context changes. This is about not having to switch contexts because your focus stays on architecture+review instead of having to do deep dives to type code around.
> Your feature branch is to put things aside and send them to CI, or wait and think on them.
No, not really. Feature branches, as well as most types of branches, is to set aside work fronts that are in progress and run in parallel.