fix: slide graphe noire + nombre slides adaptatif

- slides-renderer: SlideChart supporte le nouveau format plat
  (slide.chartType + slide.data[{label,value}]) en plus de slide.chart
  → corrige la slide noire avec légende visible mais graphe vide
- slides.tool: nombre de slides adapté au contenu
  (3-4 pour note courte, 5-7 moyenne, 8-12 longue)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memento-note/components/lab/slides-renderer.tsx

@@ -25,7 +25,18 @@ const GRID_STROKE = 'rgba(255,255,255,0.07)'
 
 // ── Chart ──────────────────────────────────────────────────────────────────────
 function SlideChart({ slide }: { slide: SlideSpec }) {
-  const { chart } = slide
+  // Support both old format (slide.chart) and new flat format (slide.chartType + slide.data)
+  const chart = slide.chart ?? (
+    slide.chartType || slide.data
+      ? {
+          type: slide.chartType ?? 'bar',
+          data: (slide.data as any[])?.map((d: any) => ({ name: d.label ?? d.name, value: d.value })) ?? [],
+          xKey: 'name',
+          yKeys: ['value'],
+          showLegend: true,
+        }
+      : undefined
+  )
   if (!chart?.data?.length) return null
 
   const colors = chart.colors ?? CHART_COLORS

memento-note/lib/ai/tools/slides.tool.ts

@@ -45,7 +45,7 @@ Available slide types:
 - "summary": title, items[] (conclusion with checkmarks)
 
 RULES:
-- 6-12 slides per presentation
+- Adapt the number of slides to the content: 3-4 slides for short notes (<200 words), 5-7 for medium, 8-12 for long/rich notes
 - First slide MUST be type "title"
 - Last slide MUST be type "summary"
 - Include at least 1 "chart" or "stats" slide