fix(glossaire): préserver les parcours intelligents explicites

Reviewed-on: #330

src/lib/glossary.ts

@@ -510,13 +510,24 @@ export function getGlossarySmartNavigation(
 ): GlossarySmartNavigation {
   const currentSlug = slugOfGlossaryEntry(currentEntry);
   const rawNavigation = currentEntry.data.navigation;
-  const defaultNavigation = GLOSSARY_NAV_DEFAULTS[familyOf(currentEntry)];
+  const defaultNavigation = GLOSSARY_NAV_DEFAULTS[familyOf(currentEntry)] ?? {};
 
-  const navigationSource = rawNavigation ?? {
-    primaryNext: undefined,
-    primaryReason: undefined,
-    paths: defaultNavigation ?? {},
-    flows: {},
+  const withDefaultPath = (
+    explicit: string[] | undefined,
+    fallback: string[] | undefined,
+  ): string[] => (explicit && explicit.length > 0 ? explicit : fallback ?? []);
+
+  const navigationSource = {
+    primaryNext: rawNavigation?.primaryNext,
+    primaryReason: rawNavigation?.primaryReason,
+    paths: {
+      understand: withDefaultPath(rawNavigation?.paths?.understand, defaultNavigation.understand),
+      deepen: withDefaultPath(rawNavigation?.paths?.deepen, defaultNavigation.deepen),
+      compare: withDefaultPath(rawNavigation?.paths?.compare, defaultNavigation.compare),
+      apply: withDefaultPath(rawNavigation?.paths?.apply, defaultNavigation.apply),
+    },
+    flows: rawNavigation?.flows ?? {},
+    relationWeights: rawNavigation?.relationWeights ?? {},
   };
 
   const primaryNext = resolveGlossaryEntriesInSourceOrder(