fix: génération asynchrone (fire-and-forget + polling)

Le problème : la route POST /api/agents/run-for-note bloquait le thread
HTTP pendant toute la durée de génération (2-5 min), provoquant un
spinner infini sans résultat.

Solution :
- POST retourne immédiatement avec { agentId } et lance executeAgent
  en arrière-plan (fire-and-forget, sans await)
- GET /api/agents/run-for-note?agentId= retourne le statut de la
  dernière agentAction (running | success | failure) + canvasId/noteId
- Le client poll le statut toutes les 3 secondes jusqu'au résultat,
  le toast persistant Sonner se met à jour automatiquement
- Cleanup du polling au démontage du composant

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/app/api/agents/run-for-note/route.ts

@@ -21,6 +21,7 @@ const TYPE_DEFAULTS: Record<GenerateType, {
   },
 }
 
+// ─── POST : kick off generation (fire-and-forget) ──────────────────────────
 export async function POST(req: NextRequest) {
   const session = await auth()
   if (!session?.user?.id) {
@@ -40,7 +41,6 @@ export async function POST(req: NextRequest) {
     return NextResponse.json({ error: 'Paramètres invalides' }, { status: 400 })
   }
 
-  // Verify note belongs to user
   const note = await prisma.note.findFirst({
     where: { id: noteId, userId },
     select: { id: true, title: true, notebookId: true },
@@ -54,7 +54,6 @@ export async function POST(req: NextRequest) {
     ? `Slides — ${(note.title || 'Note').substring(0, 40)}`
     : `Diagramme — ${(note.title || 'Note').substring(0, 40)}`
 
-  // Create a dedicated one-shot agent for this note
   const agent = await prisma.agent.create({
     data: {
       name: agentName,
@@ -72,15 +71,70 @@ export async function POST(req: NextRequest) {
     },
   })
 
-  try {
-    const { executeAgent } = await import('@/lib/ai/services/agent-executor.service')
-    const result = await executeAgent(agent.id, userId)
-    return NextResponse.json(result)
-  } catch (err) {
-    console.error('[run-for-note] executeAgent error:', err)
-    return NextResponse.json(
-      { success: false, error: err instanceof Error ? err.message : 'Erreur inconnue' },
-      { status: 500 },
-    )
-  }
+  // ── Fire and forget — do NOT await so the HTTP response returns immediately ──
+  // In Node.js / Docker self-hosted, the process keeps running after response.
+  import('@/lib/ai/services/agent-executor.service')
+    .then(({ executeAgent }) => executeAgent(agent.id, userId))
+    .catch(err => console.error('[run-for-note] Background agent error:', err))
+
+  return NextResponse.json({ success: true, agentId: agent.id, status: 'running' })
+}
+
+// ─── GET : poll current agent status ──────────────────────────────────────
+export async function GET(req: NextRequest) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Non autorisé' }, { status: 401 })
+  }
+  const userId = session.user.id
+
+  const agentId = req.nextUrl.searchParams.get('agentId')
+  if (!agentId) {
+    return NextResponse.json({ error: 'agentId manquant' }, { status: 400 })
+  }
+
+  // Verify ownership
+  const agent = await prisma.agent.findFirst({
+    where: { id: agentId, userId },
+    select: { id: true },
+  })
+  if (!agent) {
+    return NextResponse.json({ error: 'Agent introuvable' }, { status: 404 })
+  }
+
+  // Return latest action for this agent
+  const action = await prisma.agentAction.findFirst({
+    where: { agentId },
+    orderBy: { createdAt: 'desc' },
+    select: { id: true, status: true, result: true, log: true },
+  })
+
+  if (!action) {
+    // Action not created yet (race condition in first poll) — still running
+    return NextResponse.json({ status: 'running' })
+  }
+
+  // If success, find canvasId from the related canvas (result stores canvas id)
+  let canvasId: string | null = null
+  let noteId: string | null = null
+  if (action.status === 'success' && action.result) {
+    // result field: the executor stores canvas.id or note.id
+    const canvas = await prisma.canvas.findFirst({
+      where: { id: action.result },
+      select: { id: true },
+    })
+    if (canvas) {
+      canvasId = canvas.id
+    } else {
+      noteId = action.result
+    }
+  }
+
+  return NextResponse.json({
+    status: action.status,           // 'running' | 'success' | 'failure'
+    actionId: action.id,
+    canvasId,
+    noteId,
+    error: action.status === 'failure' ? (action.log || 'Erreur inconnue') : undefined,
+  })
 }