Validate module catalog provenance and availability

docs/RELEASE_DEPENDENCIES.md

@@ -221,6 +221,12 @@ Each module entry can declare:
 - WebUI package name and pinned install reference
 - `artifact_integrity` for each package, including the HTTPS registry URL,
   filename, byte size, SHA-256, package identity, source tag, and source commit
+- `source`, binding the repository and immutable tag/commit identity, with
+  optional HTTPS repository and revision links
+- `availability`, either `available` or `withdrawn`; a withdrawn entry must
+  carry an operator-readable `availability_reason` and cannot be planned
+- `configuration_requirements` and an optional HTTPS `release_notes_url` for
+  prerequisites and release-specific operator guidance
 - display metadata and tags
 - `license_features`, the feature entitlements required to plan that install
 - `dependencies` and `optional_dependencies`, the module ids expected in the
@@ -248,6 +254,12 @@ Each module entry can declare:
 - `requires_interfaces`, named interface contracts and version ranges required
   by this module
 
+Core validates these fields before exposing the directory. Admin derives a
+read-only catalog state from the installed package set, catalog dependency
+closure, named-interface providers, current-version window, availability, and
+generic license policy. This is an early operator diagnostic; trusted installer
+preflight remains the authoritative mutation gate.
+
 The signature is Ed25519 over canonical JSON with both `signature` and
 `signatures` removed. Core accepts the legacy single `signature` field and the
 new `signatures` array.