feat: AI chat tone selector + graph node pinning

- ai-chat: sélecteur tone (Professional/Créatif/Académique/Décontracté)
  passé via noteContext.tone dans le body vers /api/chat
- network-graph: dragended garde fx/fy → nœud épinglé après drag
  double-clic sur nœud pour désépingler (fx=null, fy=null)
- sprint-status: 6-2 et 6-3 passés en done

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

docs/sprint-status.yaml

@@ -64,8 +64,8 @@ development_status:
   # Epic 6 — Croissance & Activation (PLG) — ajouté 2026-05-29
   epic-6: in-progress
   6-1-onboarding-activation: done             # story-onboarding-activation.md
-  6-2-markdown-roundtrip: review        # brief-markdown-roundtrip.md
-  6-3-brainstorm-canvas-finalize: review        # story: 6-3-brainstorm-canvas-finalize.md
+  6-2-markdown-roundtrip: done        # brief-markdown-roundtrip.md
+  6-3-brainstorm-canvas-finalize: done        # story: 6-3-brainstorm-canvas-finalize.md
   6-4-chat-with-pdf: done                   # already implemented: document-qa-overlay.tsx + document-ingestion + document-search tool
   6-5-pptx-export-watermark: done              # story: 6-5-pptx-export-watermark.md
   epic-6-retrospective: optional

memento-note/components/ai-chat.tsx

@@ -42,6 +42,7 @@ export function AIChat({ showFloatingTrigger = true }: { showFloatingTrigger?: b
   const [input, setInput] = useState('')
   const [conversationId, setConversationId] = useState<string | undefined>()
   const [isContextualAIVisible, setIsContextualAIVisible] = useState(false)
+  const [tone, setTone] = useState<'professional' | 'creative' | 'academic' | 'casual'>('professional')
 
   const [history, setHistory] = useState<any[]>([])
   const [historyLoading, setHistoryLoading] = useState(false)
@@ -97,6 +98,7 @@ export function AIChat({ showFloatingTrigger = true }: { showFloatingTrigger?: b
             webSearch: webSearch && webSearchAvailable,
             conversationId: convId,
             language,
+            noteContext: { title: '', content: '', tone },
           }
         }
       )
@@ -273,6 +275,32 @@ export function AIChat({ showFloatingTrigger = true }: { showFloatingTrigger?: b
                   />
                 </div>
 
+                {/* Tone selector */}
+                <div className="flex items-center gap-1.5 flex-wrap">
+                  {(['professional', 'creative', 'academic', 'casual'] as const).map((t_) => {
+                    const labels: Record<typeof t_, string> = {
+                      professional: '💼 Pro',
+                      creative: '✨ Créatif',
+                      academic: '🎓 Académique',
+                      casual: '😊 Décontracté',
+                    }
+                    return (
+                      <button
+                        key={t_}
+                        onClick={() => setTone(t_)}
+                        className={cn(
+                          'px-2.5 py-1 rounded-full text-[10px] font-bold border transition-all',
+                          tone === t_
+                            ? 'bg-brand-accent/10 border-brand-accent/40 text-brand-accent'
+                            : 'border-border/40 text-concrete hover:border-ink/20 hover:text-ink/60'
+                        )}
+                      >
+                        {labels[t_]}
+                      </button>
+                    )
+                  })}
+                </div>
+
                 {/* Messages */}
                 {messages.length === 0 && (
                   <div className="h-48 flex flex-col items-center justify-center text-center space-y-3 text-concrete/30">

memento-note/components/network-graph.tsx

@@ -241,6 +241,11 @@ export function NetworkGraph({
         return String(d.clusterId) === selectedClusterId ? 1 : 0.15
       })
       .on('click', (event, d) => onNoteSelect(d.id))
+      .on('dblclick', (event, d) => {
+        d.fx = null
+        d.fy = null
+        simulation.alphaTarget(0.1).restart()
+      })
       .call(d3.drag<SVGGElement, D3Node>()
         .on('start', dragstarted)
         .on('drag', dragged)
@@ -328,8 +333,8 @@ export function NetworkGraph({
 
     function dragended(event: any, d: D3Node) {
       if (!event.active) simulation.alphaTarget(0)
-      d.fx = null
-      d.fy = null
+      // Garder le nœud épinglé à sa position après drag (fx/fy non remis à null)
+      // Double-clic pour désépingler → géré via dblclick ci-dessous
     }
 
     return () => {