feat(app-tauri): événements des tâches de fond exposés au front (B1-B6)

Câblage des événements de complétion/mailbox/réveil vers la couche
app-tauri pour consommation par le frontend (lots F1-F4 à venir).

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

crates/app-tauri/src/events.rs

@@ -96,6 +96,41 @@ pub enum DomainEventDto {
         /// New liveness, as a lowercase string (`"alive"` / `"stalled"`).
         liveness: AgentLivenessDto,
     },
+    /// A background task lifecycle/delivery event occurred.
+    #[serde(rename_all = "camelCase")]
+    BackgroundTaskChanged {
+        /// Project id.
+        project_id: String,
+        /// Task id.
+        task_id: String,
+        /// Owner agent id.
+        agent_id: String,
+        /// Lightweight event/state label.
+        state: String,
+    },
+    /// An agent inbox queue depth changed.
+    #[serde(rename_all = "camelCase")]
+    AgentInboxChanged {
+        /// Agent id.
+        agent_id: String,
+        /// Queue depth after the operation.
+        depth: usize,
+        /// Queue operation label.
+        action: String,
+    },
+    /// An owner wake event occurred.
+    #[serde(rename_all = "camelCase")]
+    AgentWakeChanged {
+        /// Project id.
+        project_id: String,
+        /// Agent id.
+        agent_id: String,
+        /// Wake operation label.
+        action: String,
+        /// Failure reason, when any.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        reason: Option<String>,
+    },
     /// An agent's runtime profile was changed (hot-swap of the AI engine).
     #[serde(rename_all = "camelCase")]
     AgentProfileChanged {
@@ -359,6 +394,115 @@ impl From<&DomainEvent> for DomainEventDto {
                     liveness: (*liveness).into(),
                 }
             }
+            DomainEvent::BackgroundTaskStarted {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "started".to_owned(),
+            },
+            DomainEvent::BackgroundTaskStateChanged {
+                project_id,
+                task_id,
+                owner_agent_id,
+                state,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: format!("{state:?}"),
+            },
+            DomainEvent::BackgroundTaskCompleted {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "completed".to_owned(),
+            },
+            DomainEvent::BackgroundTaskFailed {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "failed".to_owned(),
+            },
+            DomainEvent::BackgroundTaskCancelled {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "cancelled".to_owned(),
+            },
+            DomainEvent::BackgroundTaskCompletionDeliveryPending {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "deliveryPending".to_owned(),
+            },
+            DomainEvent::BackgroundTaskCompletionDelivered {
+                project_id,
+                task_id,
+                owner_agent_id,
+            } => Self::BackgroundTaskChanged {
+                project_id: project_id.to_string(),
+                task_id: task_id.to_string(),
+                agent_id: owner_agent_id.to_string(),
+                state: "delivered".to_owned(),
+            },
+            DomainEvent::AgentInboxQueued { agent_id, depth } => Self::AgentInboxChanged {
+                agent_id: agent_id.to_string(),
+                depth: *depth,
+                action: "queued".to_owned(),
+            },
+            DomainEvent::AgentInboxDrained { agent_id, depth } => Self::AgentInboxChanged {
+                agent_id: agent_id.to_string(),
+                depth: *depth,
+                action: "drained".to_owned(),
+            },
+            DomainEvent::AgentWakeScheduled {
+                project_id,
+                agent_id,
+            } => Self::AgentWakeChanged {
+                project_id: project_id.to_string(),
+                agent_id: agent_id.to_string(),
+                action: "scheduled".to_owned(),
+                reason: None,
+            },
+            DomainEvent::AgentWakeStarted {
+                project_id,
+                agent_id,
+            } => Self::AgentWakeChanged {
+                project_id: project_id.to_string(),
+                agent_id: agent_id.to_string(),
+                action: "started".to_owned(),
+                reason: None,
+            },
+            DomainEvent::AgentWakeFailed {
+                project_id,
+                agent_id,
+                reason,
+            } => Self::AgentWakeChanged {
+                project_id: project_id.to_string(),
+                agent_id: agent_id.to_string(),
+                action: "failed".to_owned(),
+                reason: Some(reason.clone()),
+            },
             DomainEvent::AgentProfileChanged {
                 agent_id,
                 profile_id,