feat(workstate): snapshot des délégations en file par agent (Lot B backend)

Ajoute un port de lecture ségrégué `AgentQueueSnapshot` (ISP) distinct du
`AgentMailbox` mutant : il expose `queue_for(agent)` qui renvoie des
`QueuedTicketSnapshot` clonés, ordonnés FIFO, avec position recalculée
(0 = tête). Observer la file ne la mute jamais ; le one-shot reply sender
reste dans l'adaptateur.

- domain : value object `QueuedTicketSnapshot` + trait `AgentQueueSnapshot`
  (object-safe, partagé en `Arc<dyn …>`).
- infrastructure : `InMemoryMailbox` implémente la vue lecture en plus de la
  vue mutation ; positions recalculées à chaque appel.
- application : le read-model work-state liste les délégations en attente via
  ce port, troncature de l'aperçu de tâche en conservant la longueur d'origine.
- app-tauri : DTO `camelCase` des tickets en file câblé dans l'état.

Tests verts : domain mailbox (6), infrastructure mailbox (13),
application workstate (12), app-tauri dto_agents (20).

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

crates/app-tauri/tests/dto_agents.rs

@@ -9,8 +9,9 @@ use app_tauri_lib::dto::{
 };
 use application::AppError;
 use application::{
-    AgentWorkState, CreateAgentOutput, InspectConversationOutput, LaunchAgentOutput,
-    ListAgentsOutput, LiveSessionKind, LiveWorkSession, ProjectWorkState,
+    AgentTicketState, AgentWorkState, CreateAgentOutput, InspectConversationOutput,
+    LaunchAgentOutput, ListAgentsOutput, LiveSessionKind, LiveWorkSession, ProjectWorkState,
+    TicketWorkSource, TicketWorkStatus,
 };
 use domain::ids::{AgentId, NodeId, ProfileId, SessionId};
 use domain::ports::ConversationDetails;
@@ -219,6 +220,7 @@ fn project_work_state_dto_serialises_live_and_busy_camelcase() {
                 ticket,
                 since_ms: 1_234,
             },
+            tickets: vec![],
         }],
     });
 
@@ -231,11 +233,77 @@ fn project_work_state_dto_serialises_live_and_busy_camelcase() {
     assert_eq!(v["agents"][0]["busy"]["state"], "busy");
     assert_eq!(v["agents"][0]["busy"]["ticket"], ticket.to_string());
     assert_eq!(v["agents"][0]["busy"]["sinceMs"], 1_234);
+    assert_eq!(v["agents"][0]["tickets"], json!([]));
     assert!(v["agents"][0].get("agent_id").is_none());
     assert!(v["agents"][0]["live"].get("session_id").is_none());
     assert!(v["agents"][0]["busy"].get("since_ms").is_none());
 }
 
+#[test]
+fn project_work_state_dto_serialises_tickets_camelcase() {
+    let agent = AgentId::from_uuid(Uuid::from_u128(11));
+    let profile = ProfileId::from_uuid(Uuid::from_u128(12));
+    let requester = AgentId::from_uuid(Uuid::from_u128(20));
+    let head_ticket = domain::TicketId::from_uuid(Uuid::from_u128(30));
+    let next_ticket = domain::TicketId::from_uuid(Uuid::from_u128(31));
+    let conversation = domain::ConversationId::from_uuid(Uuid::from_u128(40));
+    let dto = app_tauri_lib::dto::ProjectWorkStateDto::from(ProjectWorkState {
+        agents: vec![AgentWorkState {
+            agent_id: agent,
+            name: "Worker".to_owned(),
+            profile_id: profile,
+            live: None,
+            busy: domain::AgentBusyState::Idle,
+            tickets: vec![
+                AgentTicketState {
+                    ticket_id: head_ticket,
+                    conversation_id: conversation,
+                    position: 0,
+                    status: TicketWorkStatus::InProgress,
+                    source: TicketWorkSource::Agent {
+                        agent_id: requester,
+                    },
+                    requester_label: "Main".to_owned(),
+                    task_preview: "Analyser le module".to_owned(),
+                    task_len: 842,
+                },
+                AgentTicketState {
+                    ticket_id: next_ticket,
+                    conversation_id: conversation,
+                    position: 1,
+                    status: TicketWorkStatus::Queued,
+                    source: TicketWorkSource::Human,
+                    requester_label: "User".to_owned(),
+                    task_preview: "Vérifier".to_owned(),
+                    task_len: 8,
+                },
+            ],
+        }],
+    });
+
+    let v = serde_json::to_value(&dto).unwrap();
+    let head = &v["agents"][0]["tickets"][0];
+    assert_eq!(head["ticketId"], head_ticket.to_string());
+    assert_eq!(head["conversationId"], conversation.to_string());
+    assert_eq!(head["position"], 0);
+    assert_eq!(head["status"], "inProgress");
+    assert_eq!(head["source"]["kind"], "agent");
+    assert_eq!(head["source"]["agentId"], requester.to_string());
+    assert_eq!(head["requesterLabel"], "Main");
+    assert_eq!(head["taskPreview"], "Analyser le module");
+    assert_eq!(head["taskLen"], 842);
+    // snake_case must not leak.
+    assert!(head.get("ticket_id").is_none());
+    assert!(head.get("task_preview").is_none());
+    assert!(head["source"].get("agent_id").is_none());
+
+    let next = &v["agents"][0]["tickets"][1];
+    assert_eq!(next["status"], "queued");
+    assert_eq!(next["source"]["kind"], "human");
+    assert!(next["source"].get("agentId").is_none());
+    assert_eq!(next["requesterLabel"], "User");
+}
+
 #[test]
 fn launch_agent_request_carries_conversation_id_for_resume() {
     let raw = json!({