Added deterministic function layer

tests/test_builtin_extension_catalog.py

@@ -18,6 +18,7 @@ def test_builtin_extension_registry_lists_query_processors_and_backend():
     assert "runtime.form-state" in ids
     assert "runtime.assessment" in ids
     assert "policy.local-label" in ids
+    assert "document.function" in ids
 
 
 def test_builtin_processor_descriptors_capture_safety_and_provenance():
@@ -103,3 +104,22 @@ def test_builtin_policy_descriptor_exposes_cli_and_adapter_boundary():
     assert "mkt policy resource-manifest" in descriptor.cli["commands"]
     assert "IdentityClaimsAdapter" in descriptor.metadata["external_adapters"]
     assert "RelationshipPolicyAdapter" in descriptor.metadata["external_adapters"]
+
+
+def test_builtin_document_function_descriptor_exposes_deterministic_boundary():
+    registry = builtin_extension_registry()
+
+    descriptor = registry.get("document.function")
+
+    assert descriptor.kind == "document-function"
+    assert descriptor.safety["network"] is False
+    assert descriptor.metadata["external_policy_services_required"] is False
+    assert {capability.id for capability in descriptor.capabilities} >= {
+        "document_function",
+        "deterministic",
+    }
+    assert descriptor.cli["commands"] == [
+        "mkt function list",
+        "mkt function check",
+        "mkt function render",
+    ]