Migrate Distribution Lists interface patterns

docs/INTERFACE_PATTERN_MIGRATION.md

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+# Distribution Lists Interface Pattern Migration
+
+This migration applies the GovOPlaN interface pattern language to the
+distribution-list catalogue, revision editor, expansion preview, snapshot
+evidence, and reusable picker.
+
+## Surface Inventory
+
+| Surface | Archetype | Consequence class | Contract |
+| --- | --- | --- | --- |
+| `/distribution-lists` catalogue | Governed work queue | Select, create, or delete a list | Shared loading, empty, permission, disabled-reason, and help states |
+| Definition editor | Consequential definition editor | Save immutable revision | Guarded list and nested-entry drafts with contextual field semantics |
+| Expansion preview | Evidence preview | Resolve current saved revision | Explicit exclusions, provider availability, provenance, and decision explanations |
+| Frozen snapshots | Evidence register | Retain exact expansion | Immutable recipients, exclusions, source revisions, parameters, provenance, and hash |
+| Distribution-list picker | Shared object selector | Reference a list | Searchable selector with contextual definition help |
+
+## Consequence And Availability Rules
+
+- Saving creates an immutable list revision; previews and snapshots use only a
+  saved revision.
+- Include, exclude, and manual-override entries have distinct semantics. Manual
+  override requires an auditable reason.
+- Freezing is confirmed because it creates retained evidence consumed by other
+  modules. Deleting the reusable definition does not rewrite retained snapshots.
+- Provider absence is explained and never turns an optional integration into a
+  hard dependency.
+- Missing write permission and incomplete or unchanged drafts expose a reason
+  and required next action instead of a silent disabled control.
+
+Backend and WebUI manifests publish the same surface identifiers. English and
+German catalogues cover the module-owned interaction vocabulary, and contextual
+help resolves through manifest documentation rather than detached UI guidance.