A rotation the Secret Service refused lived only in the daemon's
memory, so a crash or SIGKILL before the retry landed lost the only live
refresh token.
Keep it in the kernel keyring as well until it is written. The next
resume, by the daemon or `pdfs unlock`, puts it back in when the stored
blob still holds the refresh token it spent, and writes it; one left
over from an older login is dropped. `kernelkey` now holds named keys,
the passphrases and the unsaved tokens (B61).