docs: finish zone reference hardening workplan

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a0291a-1e87-7151-9934-fcbfe3f65eb1

history/2026-08-23-retain-reference-decision.md

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+# Retain the offline reference repository — 2026-08-23
+
+**Decision:** retain `zone-engine` as an offline reference-conformance
+repository while `security-zones_v0.1` remains proposed in net-kingdom canon.
+
+**Authority:** zone-engine owner under the operator-directed execution of
+`ZONE-WP-0002`; canon and control ownership remain unchanged.
+
+## Maintenance contract
+
+- Maintainer: zone-engine.
+- Authoritative standard: net-kingdom canon, never the local pointer.
+- Allowed changes: canon-lineage refresh, conformance fixtures, and a concrete
+  revision requested by canon or an adopting control owner.
+- Forbidden expansion: runtime/API/storage, live policy decisions, implicit
+  workload discovery, central exception enforcement, or local stance authority.
+- Routine backlog: none.
+
+## Archive triggers
+
+Reassess archival when any of the following is true:
+
+1. net-kingdom accepts or supersedes v0.1 and owns the durable conformance
+   assets;
+2. the adopting control owners absorb the fixtures and no shared reference is
+   needed; or
+3. no adopting control depends on this reference surface.
+
+Archiving or renaming the Forgejo repository remains an attended operator
+action. This decision deliberately performs neither.