Add render reference asset manifest contract

tests/test_builtin_extension_catalog.py

@@ -25,6 +25,7 @@ def test_builtin_extension_registry_lists_query_processors_and_backend():
     assert "memory.runtime-adapter-boundary" in ids
     assert "memory.context-package" in ids
     assert "render.export-registry" in ids
+    assert "render.reference-manifest" in ids
     assert "render.fake" in ids
     assert "source.adapter-registry" in ids
 
@@ -190,11 +191,16 @@ def test_builtin_render_export_descriptors_expose_contract_boundary():
     registry = builtin_extension_registry()
 
     registry_descriptor = registry.get("render.export-registry")
+    reference_manifest = registry.get("render.reference-manifest")
     fake = registry.get("render.fake")
 
     assert registry_descriptor.kind == "render-export-registry"
     assert registry_descriptor.safety["external_process"] is False
     assert registry_descriptor.metadata["concrete_renderer_execution_required"] is False
+    assert reference_manifest.kind == "render-reference-contract"
+    assert reference_manifest.safety["asset_copying"] is False
+    assert reference_manifest.safety["final_numbering"] is False
+    assert reference_manifest.metadata["core_performs_asset_copying"] is False
     assert fake.kind == "render-export"
     assert fake.safety["external_process"] is False
     assert fake.safety["filesystem_write"] is False