Fix 404 chapitres : stem Nuxt Content inclut le dossier parent

Le `chapter.stem` de Nuxt Content renvoie `book/01-introduction` et non
`01-introduction`. Extraction du slug final via `.split('/').pop()` dans
les liens et la navigation prev/next.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/pages/modele-eco/[slug].vue

@@ -14,7 +14,7 @@
     <nav class="mt-16 flex items-center justify-between border-t border-white/8 pt-8">
       <NuxtLink
         v-if="prevChapter"
-        :to="`/modele-eco/${prevChapter.stem}`"
+        :to="`/modele-eco/${prevChapter.stem?.split('/').pop()}`"
         class="btn-ghost gap-2"
       >
         <div class="i-lucide-arrow-left h-4 w-4" />
@@ -24,7 +24,7 @@
 
       <NuxtLink
         v-if="nextChapter"
-        :to="`/modele-eco/${nextChapter.stem}`"
+        :to="`/modele-eco/${nextChapter.stem?.split('/').pop()}`"
         class="btn-ghost gap-2"
       >
         <span class="text-sm">{{ nextChapter.title }}</span>
@@ -64,7 +64,7 @@ const { data: allChapters } = await useAsyncData('book-nav', () =>
 )
 
 const currentIndex = computed(() =>
-  allChapters.value?.findIndex(c => c.stem === slug) ?? -1,
+  allChapters.value?.findIndex(c => c.stem?.split('/').pop() === slug) ?? -1,
 )
 
 const prevChapter = computed(() => {

app/pages/modele-eco/index.vue

@@ -91,7 +91,7 @@
             :key="chapter.path"
           >
             <NuxtLink
-              :to="`/modele-eco/${chapter.stem}`"
+              :to="`/modele-eco/${chapter.stem?.split('/').pop()}`"
               class="card-surface flex items-start gap-4 group"
             >
               <span class="font-mono text-2xl font-bold text-primary/30 leading-none mt-1 w-10 text-right flex-shrink-0">
@@ -109,7 +109,7 @@
                     <span class="i-lucide-clock inline-block h-3 w-3 mr-1 align-middle" />
                     {{ chapter.readingTime }}
                   </span>
-                  <SongBadges :chapter-slug="chapter.stem!" />
+                  <SongBadges :chapter-slug="chapter.stem?.split('/').pop() ?? ''" />
                 </div>
               </div>
               <div class="i-lucide-chevron-right h-5 w-5 text-white/20 group-hover:text-primary/60 transition-colors flex-shrink-0 mt-2" />