Restores the kernel-level isolation the pre-cutover ttyd-session.sh had,
but keeps the multi-session lobby UX:
- ttyd.service gets `-H X-authentik-username` back. `tmux-attach.sh` reads
$TTYD_USER, looks up the local part in /etc/ttyd-user-map, denies the
connection (no fallback to wizard) if there's no mapping, otherwise
`sudo -n -H -u <os_user> tmux …`. Each Authentik identity → its own
Unix user → its own `/tmp/tmux-<uid>/default` socket.
- tmux-api scopes every request to the same OS user via the same header.
Adds /whoami so the lobby HTML can preflight access and render
"logged in as <os_user> (<authentik>)" instead of leaving the user to
discover the deny via a reconnect loop.
- Commits /etc/ttyd-user-map and the matching /etc/sudoers.d/ttyd-users
fragment under files/devvm/ so future operators see one canonical
source of truth. Current mappings: vbarzin → wizard, emil.barzin → emo.
Adding a user is now: append a line to ttyd-user-map + a NOPASSWD
sudoers line + `useradd -m`. README walks through it.
No Terraform changes — this is all DevVM-side + lobby JS.
