feat: harden shared platform contracts

tests/test_documentation_topic_contract.py

@@ -3,7 +3,10 @@ from __future__ import annotations
 import unittest
 
 from govoplan_core.core.modules import (
+    DocumentationConfigurationDecision,
+    DocumentationConfigurationProviderRegistration,
     DocumentationCondition,
+    DocumentationSourceDefinition,
     DocumentationTopic,
     ModuleManifest,
     user_workflow_scope_condition_issues,
@@ -67,6 +70,52 @@ class DocumentationTopicContractTests(unittest.TestCase):
         self.assertEqual(user_workflow_scope_condition_issues(user_reference), ())
         registry_for(scoped, admin_workflow, user_reference).validate()
 
+    def test_documentation_configuration_and_source_extensions_are_validated(self) -> None:
+        resolver = lambda _context, keys: {  # noqa: E731
+            key: DocumentationConfigurationDecision(key=key, state="enabled")
+            for key in keys
+        }
+        registry = PlatformRegistry()
+        registry.register(ModuleManifest(
+            id="example",
+            name="Example",
+            version="1.0.0",
+            documentation_configuration_providers=(
+                DocumentationConfigurationProviderRegistration(
+                    keys=("example.feature",),
+                    resolve=resolver,
+                ),
+            ),
+            documentation_sources=(
+                DocumentationSourceDefinition(
+                    id="example.handbook",
+                    kind="repository",
+                    label="Example handbook",
+                ),
+            ),
+        ))
+
+        registry.validate()
+
+        duplicate = PlatformRegistry()
+        duplicate.register(ModuleManifest(
+            id="example",
+            name="Example",
+            version="1.0.0",
+            documentation_configuration_providers=(
+                DocumentationConfigurationProviderRegistration(
+                    keys=("example.feature",),
+                    resolve=resolver,
+                ),
+                DocumentationConfigurationProviderRegistration(
+                    keys=("example.feature",),
+                    resolve=resolver,
+                ),
+            ),
+        ))
+        with self.assertRaisesRegex(RegistryError, "duplicate documentation configuration key"):
+            duplicate.validate()
+
 
 def registry_for(*topics: DocumentationTopic) -> PlatformRegistry:
     registry = PlatformRegistry()