fix: runAgent fire-and-forget + polling sur la page /agents

Le bouton Play des cartes agents appelait runAgent (Server Action) qui
attendait executeAgent (~2-5 min) → spinner bloqué sans résultat.

- runAgent retourne immédiatement { success, agentId }
- agent-card.tsx lance un polling toutes les 3s sur GET
  /api/agents/run-for-note?agentId= jusqu'au statut terminal
- Toast persistant Sonner pendant la génération, mis à jour au résultat
- Cleanup automatique du polling au démontage

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

memento-note/components/agents/agent-card.tsx

@@ -5,7 +5,7 @@
  * Compact card matching the reference design — with a "Next Run / Status" footer.
  */
 
-import { useState, useEffect } from 'react'
+import { useState, useEffect, useRef } from 'react'
 import { formatDistanceToNow } from 'date-fns'
 import { fr } from 'date-fns/locale/fr'
 import { enUS } from 'date-fns/locale/en-US'
@@ -83,21 +83,51 @@ export function AgentCard({ agent, onEdit, onRefresh, onToggle }: AgentCardProps
   const dateLocale = language === 'fr' ? fr : enUS
   const isNew = Date.now() - new Date(agent.createdAt).getTime() < 5 * 60 * 1000
 
+  const pollRef = useRef<ReturnType<typeof setInterval> | null>(null)
+
+  // Cleanup polling on unmount
+  useEffect(() => () => { if (pollRef.current) clearInterval(pollRef.current) }, [])
+
   const handleRun = async () => {
     setIsRunning(true)
+    const toastId = toast.loading(
+      t('agents.toasts.running') || `Agent "${agent.name}" en cours…`,
+      { description: t('agents.toasts.runningDesc') || 'La génération peut prendre quelques minutes.', duration: Infinity }
+    )
     try {
       const { runAgent } = await import('@/app/actions/agent-actions')
       const result = await runAgent(agent.id)
-      if (result.success) {
-        toast.success(t('agents.toasts.runSuccess', { name: agent.name }))
-      } else {
-        toast.error(t('agents.toasts.runError', { error: result.error || t('agents.toasts.runFailed') }))
+      if (!result.success) {
+        toast.error(t('agents.toasts.runError', { error: result.error || t('agents.toasts.runFailed') }), { id: toastId })
+        setIsRunning(false)
+        return
       }
+
+      // Poll status every 3 s until terminal state
+      if (pollRef.current) clearInterval(pollRef.current)
+      pollRef.current = setInterval(async () => {
+        try {
+          const res = await fetch(`/api/agents/run-for-note?agentId=${agent.id}`)
+          const data = await res.json()
+          if (data.status === 'success') {
+            clearInterval(pollRef.current!)
+            pollRef.current = null
+            setIsRunning(false)
+            toast.success(t('agents.toasts.runSuccess', { name: agent.name }), { id: toastId, duration: 6000 })
+            onRefresh()
+          } else if (data.status === 'failure') {
+            clearInterval(pollRef.current!)
+            pollRef.current = null
+            setIsRunning(false)
+            toast.error(t('agents.toasts.runError', { error: data.error || t('agents.toasts.runFailed') }), { id: toastId })
+            onRefresh()
+          }
+        } catch { /* network error — keep polling */ }
+      }, 3000)
+
     } catch {
-      toast.error(t('agents.toasts.runGenericError'))
-    } finally {
+      toast.error(t('agents.toasts.runGenericError'), { id: toastId })
       setIsRunning(false)
-      onRefresh()
     }
   }