A module can declare state but not a step that runs. mosquitto must seed its
dynsec admin into dynamic-security.json before the broker starts, or the plugin
aborts; the database providers need the same for first-boot migrations and
health gates (04-ISSUES/037). The old event-hook engine that did this was
powerful and flaky; this is the narrowest sound mechanism instead.
A run-once step is an ordinary container marked `run-once: true`: the host runs
it to completion, requires exit 0, and gates the apply on it — so what the
declaration places after it (the broker) starts only once it has finished.
Gating is by declaration order, not a resolved dependency (ADR 0005); the
completion marker is the recorded declaration digest (ADR 0018), so a re-apply
does not re-run it unless the declaration changed. No new host shape and no
arbitrary host command: strictly less powerful than an `action`.
Points 04-ISSUES/037 fixed-by/amended-design at the record; index regenerated;
records.py and index.py pass.
Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF
jschoubben