Use the Windows ssh-agent in WSL without breaking auto-poweroff

I prefer WSL to shut down when I close the last terminal. I also want easy access to the keys I keep in my Windows ssh-agent. For a long time, trying to get both meant compromising. I tried a few hacks that kept WSL running forever, forcing me to always remember to manually terminate the WSL session. I finally settled on a tidy user-scoped bridge. It gives WSL access to the Windows agent and still…