feat(frontend): surface UI des tâches de fond (F1-F4)

Expose les tâches de fond côté front : modèle domaine et
normalisation du work state, panneau ProjectWorkStatePanel,
intégration dans LayoutGrid et ProjectsView, et abonnement aux
événements backgroundTaskChanged / agentInboxChanged /
agentWakeChanged pour rafraîchir l'état. npm run build + npm test
(449) verts.

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

frontend/src/domain/index.ts

@@ -20,6 +20,26 @@ export type DomainEvent =
   | { type: "agentExited"; agentId: string; code: number }
   | { type: "agentProfileChanged"; agentId: string; profileId: string }
   | { type: "agentBusyChanged"; agentId: string; busy: boolean }
+  | {
+      type: "backgroundTaskChanged";
+      projectId: string;
+      taskId: string;
+      agentId: string;
+      state: string;
+    }
+  | {
+      type: "agentInboxChanged";
+      agentId: string;
+      depth: number;
+      action: string;
+    }
+  | {
+      type: "agentWakeChanged";
+      projectId: string;
+      agentId: string;
+      action: string;
+      reason?: string;
+    }
   | {
       /**
        * A delegation is ready to be injected into the agent's native terminal
@@ -170,6 +190,31 @@ export interface AgentTicketState {
   taskLen: number;
 }
 
+/** One first-class background task visible in the work-state read-model. */
+export interface BackgroundCompletion {
+  taskId: string;
+  ownerAgentId: string;
+  projectId: string;
+  kind: string;
+  status: "running" | "completed" | "failed" | "cancelled" | "pending" | "delivered";
+  exitCode: number | null;
+  stdoutTail: string | null;
+  stderrTail: string | null;
+  finishedAtMs: number | null;
+}
+
+/** One item currently pending in an agent's inbox. */
+export interface InboxItem {
+  id: string;
+  agentId: string;
+  source: string;
+  kind: string;
+  body: string;
+  createdAtMs: number;
+  correlationId?: string;
+  priority: number;
+}
+
 /** Availability of a compact conversation summary in the work-state read-model. */
 export type ConversationPreviewStatus =
   | "ready"
@@ -205,6 +250,9 @@ export interface AgentWorkState {
   live?: LiveWorkSession;
   busy: WorkBusyState;
   tickets: AgentTicketState[];
+  inboxDepth?: number;
+  inbox?: InboxItem[];
+  backgroundTasks?: BackgroundCompletion[];
 }
 
 /** Minimal read-only live-state surface for a project. */