Complete REUSE-WP-0005: registry federation and relation graphs

Add federation manifest and schema, federation compose and graph CLI commands,
relation cycle/reference checks, federated index and Mermaid graph artifacts,
RegistryFederation guide, and CI validation updates.

registry/README.md

@@ -31,7 +31,7 @@ registry/
    - `external_evidence.completeness.level: C0`
    - `external_evidence.reliability.level: R0`
 4. Add the entry to `registry/indexes/capabilities.yaml`.
-5. Run the manual validation checklist below.
+5. Run `reuse-surface validate --relations` and `reuse-surface federation compose`.
 
 Missing evidence is acceptable in the MVP when it is explicit rather than hidden.
 
@@ -129,6 +129,17 @@ Check for overlap in:
 When overlap is real, link entries with `relations.related_to`, `specializes`,
 or `generalizes` rather than creating silent duplicates.
 
+## Relation graph
+
+Regenerate the Mermaid graph after relation changes:
+
+```bash
+reuse-surface graph
+reuse-surface graph --check
+```
+
+Output: `docs/graph/capability-graph.mmd`
+
 ## Promote a capability
 
 1. Attach evidence appropriate to the target level in
@@ -137,5 +148,6 @@ or `generalizes` rather than creating silent duplicates.
 3. Append a `promotion_history` record with `date`, `dimension`, `from`, `to`,
    and `rationale` (optional `author`).
 4. Update `availability.current_artifacts` when a new consumption mode appears.
-5. Refresh the index `vector` and run `reuse-surface validate`.
+5. Refresh the index `vector` and run `reuse-surface validate --relations`.
+6. Run `reuse-surface federation compose` and `reuse-surface graph`.
 6. Set `status: reviewed` or `approved` when an assessor validates the entry.