feat(memory): config embedders (LOT C2) + suggestion contextuelle (LOT C3) + contexte projet partagé

- LOT C2 (§14.5.3) : use cases de configuration des embedders déclaratifs
  (List/Save/Delete + DescribeEmbedderEngines : modèles ONNX recommandés,
  environnement local détecté, stratégies compilées). UI EmbedderSettings.
- LOT C3 (§14.5.5) : suggestion contextuelle best-effort à l'activation quand la
  mémoire dépasse le budget de recall sans embedder configuré (event
  EmbedderSuggested, anti-spam 1×/session, « ne plus demander »).
- Contexte projet partagé .ideai/CONTEXT.md (model-agnostic) injecté à tous les
  agents/profils au lancement, avant la persona. UI ProjectContextPanel.

Tests : backend workspace vert (0 échec) ; frontend 306/306.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/agents/AgentsPanel.tsx

@@ -116,6 +116,7 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
    * set by the hook once launchAgent resolves.
    */
   const [activeAgentId, setActiveAgentId] = useState<string | null>(null);
+  const [panelNodeIds, setPanelNodeIds] = useState<Record<string, string>>({});
 
   /**
    * Live PTY session id of the running agent terminal, keyed by agent id. Lets
@@ -149,11 +150,15 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
   }
 
   function handleLaunch(agentId: string) {
+    setPanelNodeIds((prev) => ({
+      ...prev,
+      [agentId]: prev[agentId] ?? crypto.randomUUID(),
+    }));
     setActiveAgentId(agentId);
   }
 
-  function handleStop() {
-    vm.stopAgent();
+  function handleStop(agentId?: string) {
+    void vm.stopAgent(agentId);
     setActiveAgentId(null);
   }
 
@@ -288,6 +293,7 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
             {vm.agents.map((a) => {
               const isSelected = a.id === vm.selectedAgentId;
               const isRunning = a.id === activeAgentId;
+              const live = vm.liveAgents.find((candidate) => candidate.agentId === a.id);
               const profileName =
                 vm.profiles.find((p) => p.id === a.profileId)?.name ??
                 a.profileId;
@@ -318,6 +324,11 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
                       )}
                     </span>
                     <span className="text-xs text-muted">{profileName}</span>
+                    {live && (
+                      <span className="text-xs text-primary">
+                        running in IdeA · {live.sessionId ?? live.nodeId}
+                      </span>
+                    )}
                   </button>
 
                   <div className="flex items-center gap-1.5 shrink-0">
@@ -334,12 +345,12 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
                         Sync
                       </Button>
                     )}
-                    {isRunning ? (
+                    {isRunning || live ? (
                       <Button
                         size="sm"
                         variant="ghost"
                         aria-label={`stop ${a.name}`}
-                        onClick={handleStop}
+                        onClick={() => handleStop(a.id)}
                         className="text-danger hover:text-danger"
                       >
                         Stop
@@ -381,7 +392,11 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
               key={activeAgentId}
               cwd={projectRoot}
               open={(opts, onData) =>
-                vm.launchAgent(activeAgentId, opts, onData)
+                vm.launchAgent(
+                  activeAgentId,
+                  { ...opts, nodeId: panelNodeIds[activeAgentId] },
+                  onData,
+                )
               }
               reattach={(sessionId, onData) =>
                 gateways.agent.reattach(sessionId, onData)