feat(core): add structured documentation localization contract

src/govoplan_core/core/modules.py

@@ -289,6 +289,30 @@ DocumentationSourceState = Literal["configured", "disabled", "unavailable"]
 CapabilityStability = Literal["experimental", "stable", "deprecated"]
 
 
+DOCUMENTATION_STRUCTURED_TRANSLATION_VERSION = "1"
+DOCUMENTATION_LOCALIZABLE_METADATA_KEYS = frozenset(
+    {
+        "admin_explanation",
+        "consequence_classes",
+        "consequences",
+        "constraints",
+        "current_configuration",
+        "fields",
+        "limitations",
+        "operational_consequences",
+        "outcome",
+        "prerequisites",
+        "privacy_notes",
+        "purpose",
+        "result",
+        "steps",
+        "user_explanation",
+        "verification",
+        "when_used",
+    }
+)
+
+
 @dataclass(frozen=True, slots=True)
 class DocumentationLink:
     label: str
@@ -324,12 +348,142 @@ class DocumentationTopic:
     configuration_keys: tuple[str, ...] = ()
     i18n_key: str | None = None
     translations: Mapping[str, Mapping[str, str]] = field(default_factory=dict)
+    structured_translation_version: str | None = None
+    structured_translations: Mapping[str, Mapping[str, Any]] = field(
+        default_factory=dict
+    )
     source_module_id: str | None = None
     version_min: str | None = None
     version_max_exclusive: str | None = None
     metadata: Mapping[str, Any] = field(default_factory=dict)
 
 
+def localizable_documentation_metadata_keys(
+    topic: DocumentationTopic,
+) -> tuple[str, ...]:
+    """Return structured metadata keys whose values are public prose."""
+
+    return tuple(
+        sorted(DOCUMENTATION_LOCALIZABLE_METADATA_KEYS.intersection(topic.metadata))
+    )
+
+
+def localized_documentation_metadata(
+    topic: DocumentationTopic,
+    locale: str,
+) -> dict[str, Any]:
+    """Overlay one validated structured translation onto source metadata."""
+
+    localized = dict(topic.metadata)
+    translation = topic.structured_translations.get(locale)
+    if translation:
+        localized.update(translation)
+    return localized
+
+
+def documentation_structured_translation_issues(
+    topic: DocumentationTopic,
+) -> tuple[str, ...]:
+    """Validate the opt-in, versioned structured-documentation translation."""
+
+    version = topic.structured_translation_version
+    translations = topic.structured_translations
+    if version is None:
+        if translations:
+            return (
+                "structured_translations require structured_translation_version",
+            )
+        return ()
+    if version != DOCUMENTATION_STRUCTURED_TRANSLATION_VERSION:
+        return (
+            "unsupported structured_translation_version "
+            f"{version!r}; expected {DOCUMENTATION_STRUCTURED_TRANSLATION_VERSION!r}",
+        )
+
+    localizable_keys = set(localizable_documentation_metadata_keys(topic))
+    issues: list[str] = []
+    for locale, translation in translations.items():
+        if not locale.strip():
+            issues.append("structured translation locale must not be empty")
+            continue
+        translated_keys = set(translation)
+        for key in sorted(translated_keys - localizable_keys):
+            issues.append(
+                f"structured translation {locale!r} contains non-localizable or missing metadata key {key!r}"
+            )
+        for key in sorted(localizable_keys - translated_keys):
+            issues.append(
+                f"structured translation {locale!r} is missing metadata key {key!r}"
+            )
+        for key in sorted(localizable_keys & translated_keys):
+            issues.extend(
+                _structured_translation_shape_issues(
+                    topic.metadata[key],
+                    translation[key],
+                    path=f"{locale}.{key}",
+                )
+            )
+    return tuple(issues)
+
+
+def _structured_translation_shape_issues(
+    source: object,
+    translated: object,
+    *,
+    path: str,
+) -> tuple[str, ...]:
+    if isinstance(source, str):
+        if not isinstance(translated, str) or not translated.strip():
+            return (f"structured translation {path} must be a non-empty string",)
+        return ()
+    if isinstance(source, Mapping):
+        if not isinstance(translated, Mapping):
+            return (f"structured translation {path} must preserve object shape",)
+        issues: list[str] = []
+        source_keys = {str(key) for key in source}
+        translated_keys = {str(key) for key in translated}
+        if source_keys != translated_keys:
+            issues.append(
+                f"structured translation {path} must preserve object keys"
+            )
+            return tuple(issues)
+        for key, value in source.items():
+            issues.extend(
+                _structured_translation_shape_issues(
+                    value,
+                    translated[key],
+                    path=f"{path}.{key}",
+                )
+            )
+        return tuple(issues)
+    if isinstance(source, Sequence) and not isinstance(
+        source, (str, bytes, bytearray)
+    ):
+        if not isinstance(translated, Sequence) or isinstance(
+            translated, (str, bytes, bytearray)
+        ):
+            return (f"structured translation {path} must preserve list shape",)
+        if len(source) != len(translated):
+            return (f"structured translation {path} must preserve list length",)
+        issues: list[str] = []
+        for index, (source_item, translated_item) in enumerate(
+            zip(source, translated, strict=True)
+        ):
+            issues.extend(
+                _structured_translation_shape_issues(
+                    source_item,
+                    translated_item,
+                    path=f"{path}[{index}]",
+                )
+            )
+        return tuple(issues)
+    if translated != source:
+        return (
+            f"structured translation {path} must preserve non-text value {source!r}",
+        )
+    return ()
+
+
 def user_workflow_scope_condition_issues(topic: DocumentationTopic) -> tuple[str, ...]:
     """Return fail-closed authoring issues for a user-facing workflow topic.
 

src/govoplan_core/core/registry.py

@@ -26,6 +26,7 @@ from govoplan_core.core.modules import (
     TenantSummaryBatchProvider,
     TenantSummaryProvider,
     user_workflow_scope_condition_issues,
+    documentation_structured_translation_issues,
 )
 from govoplan_core.core.module_entitlements import (
     TenantModuleEntitlementResolver,
@@ -962,6 +963,10 @@ def _validate_manifest_shape(manifest: ModuleManifest) -> None:
             raise RegistryError(
                 f"Module {manifest.id!r} documentation topic {topic.id!r}: {issue}"
             )
+        for issue in documentation_structured_translation_issues(topic):
+            raise RegistryError(
+                f"Module {manifest.id!r} documentation topic {topic.id!r}: {issue}"
+            )
     _validate_documentation_extensions(manifest)
     _validate_architecture_declarations(manifest)
     _validate_workflow_definition_contributions(manifest)