The runtime stage of Containerfile.engine ran `adduser --system …`. The pinned
ubuntu:24.04 base ships no adduser, so the build died at that RUN line with
crun's "executable file not found in $PATH".
Verified in the base itself on Dankclaw, 2026-10-18: `command -v adduser`
prints nothing, and the exact replacement line — `useradd --system --uid 10000
--home-dir /app --shell /usr/sbin/nologin tts` — answers `uid=10000(tts)
gid=999(tts)`. Same account as before: numeric uid/gid 10000, non-login shell,
no password entry. Its one warning ("uid 10000 is greater than SYS_UID_MAX
999") is cosmetic and is what keeps the uid equal to the façade's, so the
comment says so before someone "fixes" it by dropping --system.