Plan ConfigKit adoption and clarify implementation policy

docs/policy/documentation.md

@@ -30,6 +30,18 @@ that the behavior exists. The roadmap owns implementation status and sequencing
 until the decision is implemented. Current architecture, user, operator,
 integration, and internal documentation are updated when the behavior lands.
 
+### Implementation Details And Policy
+
+Documentation must distinguish an explicit contract from an incidental
+implementation choice. Do not describe a restriction, guarantee, security
+policy, default, or limit as authoritative merely because the current code
+implements it. Documentation may accurately describe current behavior without
+making it a permanent requirement; distinguish descriptive behavior from
+normative policy. The
+[implementation-discipline rules](architecture.md#implementation-discipline)
+own the criteria for adopting product restrictions and for elevating behavior
+into repository policy.
+
 ### Audience And Detail
 
 Write for the document's stated audience and include only the detail needed for