authenticate() cannot tell "no such session" from "the session lookup
failed" on its own — both arrive as an error. Answering 401 for both
meant a disk or file-permission problem presented as every session
ending at once: the frontend clears its state and shows the sign-in
screen to everybody, and the logs record a wave of failed logins rather
than the fault.
Now only a missing or unknown credential is 401. Anything else is a 500
and is logged as what it is.
Found while writing the smoke tests, where a deleted database file
produced SQLITE_CANTOPEN on the connections that had not been opened
yet — so most requests succeeded and a few reported the user as signed
out, which reads exactly like a flaky auth bug.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
