Add repo-family metadata to Fabric registry

docs/registry-onboarding.md

@@ -45,6 +45,7 @@ repositories:
     path: ..
     default_branch: main
     state_hub_repo_id: 2c0de614-e468-4eb6-8157-470649ac8c05
+    repo_family: ownership
     declaration_paths:
       - ..
     sbom: bom.json
@@ -58,6 +59,17 @@ repositories:
 link back to State Hub repo views, but do not block onboarding when a repo is
 registered in Fabric before that ID is wired in here.
 
+The following repo-family metadata fields are also optional:
+
+- `repo_family`: `ownership`, `rail`, `rapp`, or `reef`
+- `ownership_repo`: canonical owning `railiance-*` repo when the registered repo
+  is not itself an ownership repo
+- `primary_rail`: default rail for a reef or package when one is explicitly
+  declared
+- `supported_rails`: array of supported rail ids for `rapp-*` repos
+- `substrate_kind`: grouped substrate category such as `server`,
+  `workstation-group`, or `cluster`
+
 `sbom` or `sboms` may point to CycloneDX JSON/YAML files. When present, the
 command ingests them as queryable library inventory after repository
 registration.