The updater was emitted from a heredoc inside the installer, so a container
provisioned before it existed had no way to obtain /usr/bin/update — 'update'
just reported command not found, with no path forward short of reinstalling.
Ship it as deploy/install/metervault-update.sh and have the installer
install(1) it from the checkout it just built. An already-provisioned
container can now bootstrap from its own source tree after a git pull, and the
updater refreshes itself (atomic rename, since bash reads a running script
lazily) so the same stranding does not recur.
Uses echo rather than msg_warn for the missing-file case: msg_warn is not
otherwise relied on in this script, and an undefined function under the
framework ERR trap would abort an otherwise-successful install.
Claude-Session: https://claude.ai/code/session_01V6joyergfvVLFEizH1hJLd
