fix: a shell opens without the password and code again while the user's last use of a shell is within web.shell_auth_timeout minutes.

ADR.md

@@ -909,7 +909,10 @@ Manager cannot set it. The shell runs as the console account of the signed-in us
 it is never root and each administrator's shell is the administrator's own; a user without
 console login gets none. `POST /shell` signs the user in again with the password
 and TOTP code and gives a one-time ticket valid 30 seconds; a WebSocket on `GET /shell` with that
-ticket gets the shell. The WebSocket of RFC 6455 is implemented on the standard library inside the
+ticket gets the shell. Asking for the password and code at every opening of the page is tiresome,
+so within `web.shell_auth_timeout` minutes of the user's last sign-in or keystroke a ticket is given
+without them; the times are kept in the web service's memory only, so a restart asks again, and 0
+keeps the sign-in at every opening. The WebSocket of RFC 6455 is implemented on the standard library inside the
 web service's `http.server`, server side only, without extensions. `systemd-run --pty` starts the
 shell in a transient unit with a PAM login session, outside the sandbox, and `setsid --ctty`
 makes the terminal its controlling terminal so window sizes reach the shell. A shell idle for