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/src/dto.rs

@@ -9,8 +9,9 @@
 use serde::{Deserialize, Serialize};
 
 use application::{
-    AppError, CreateProjectInput, CreateProjectOutput, GitGraphOutput, HealthInput, HealthReport,
-    LayoutKind, ListProjectsOutput, LiveSessionKind, OpenProjectOutput, ProjectWorkState,
+    AgentTicketState, AppError, CreateProjectInput, CreateProjectOutput, GitGraphOutput,
+    HealthInput, HealthReport, LayoutKind, ListProjectsOutput, LiveSessionKind, OpenProjectOutput,
+    ProjectWorkState, TicketWorkSource, TicketWorkStatus,
 };
 use domain::{AgentBusyState, Project, ProjectId};
 
@@ -1503,6 +1504,87 @@ pub struct LiveWorkSessionDto {
     pub kind: LiveWorkSessionKindDto,
 }
 
+/// Derived processing status of a queued ticket.
+#[derive(Debug, Clone, Copy, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum TicketWorkStatusDto {
+    /// The agent's current busy turn is running this ticket.
+    InProgress,
+    /// Waiting behind the head / the agent is idle.
+    Queued,
+}
+
+impl From<TicketWorkStatus> for TicketWorkStatusDto {
+    fn from(status: TicketWorkStatus) -> Self {
+        match status {
+            TicketWorkStatus::InProgress => Self::InProgress,
+            TicketWorkStatus::Queued => Self::Queued,
+        }
+    }
+}
+
+/// Origin of a queued ticket (human operator or a delegating agent).
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase", tag = "kind")]
+pub enum TicketWorkSourceDto {
+    /// The human operator.
+    Human,
+    /// Another agent delegating via `idea_ask_agent`.
+    #[serde(rename_all = "camelCase")]
+    Agent {
+        /// The delegating agent id.
+        agent_id: String,
+    },
+}
+
+impl From<TicketWorkSource> for TicketWorkSourceDto {
+    fn from(source: TicketWorkSource) -> Self {
+        match source {
+            TicketWorkSource::Human => Self::Human,
+            TicketWorkSource::Agent { agent_id } => Self::Agent {
+                agent_id: agent_id.to_string(),
+            },
+        }
+    }
+}
+
+/// One queued/in-progress delegation ticket for an agent.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct AgentTicketStateDto {
+    /// Stable id of the queued ticket.
+    pub ticket_id: String,
+    /// Conversation thread this task enters.
+    pub conversation_id: String,
+    /// FIFO position at snapshot time (`0` = head).
+    pub position: u32,
+    /// Derived status (in-progress vs queued).
+    pub status: TicketWorkStatusDto,
+    /// Origin of the ticket.
+    pub source: TicketWorkSourceDto,
+    /// Display label of the requester.
+    pub requester_label: String,
+    /// Bounded excerpt of the task.
+    pub task_preview: String,
+    /// Character length of the original (un-truncated) task.
+    pub task_len: usize,
+}
+
+impl From<AgentTicketState> for AgentTicketStateDto {
+    fn from(ticket: AgentTicketState) -> Self {
+        Self {
+            ticket_id: ticket.ticket_id.to_string(),
+            conversation_id: ticket.conversation_id.to_string(),
+            position: ticket.position,
+            status: ticket.status.into(),
+            source: ticket.source.into(),
+            requester_label: ticket.requester_label,
+            task_preview: ticket.task_preview,
+            task_len: ticket.task_len,
+        }
+    }
+}
+
 /// One manifest agent's current live/busy state.
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
@@ -1517,6 +1599,8 @@ pub struct AgentWorkStateDto {
     pub live: Option<LiveWorkSessionDto>,
     /// Current mediated-input busy state.
     pub busy: AgentBusyState,
+    /// Pending/in-progress delegation tickets, in FIFO order.
+    pub tickets: Vec<AgentTicketStateDto>,
 }
 
 /// Project-level read model for conversation/delegation UX.
@@ -1543,6 +1627,11 @@ impl From<ProjectWorkState> for ProjectWorkStateDto {
                         kind: live.kind.into(),
                     }),
                     busy: agent.busy,
+                    tickets: agent
+                        .tickets
+                        .into_iter()
+                        .map(AgentTicketStateDto::from)
+                        .collect(),
                 })
                 .collect(),
         }