feat(workstate): résumés de conversation dans le read-model (Lot C backend)

Étend le read-model work-state pour exposer un résumé par conversation
(participants, dernier message/activité, compteurs) câblé jusqu'au DTO
camelCase de l'état app-tauri.

- application : assemblage des résumés de conversation dans le work-state.
- app-tauri : DTO camelCase des résumés + exposition dans l'état.

Tests verts : application workstate (21), app-tauri dto_agents (21),
aucun warning Rust.

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

crates/app-tauri/src/dto.rs

@@ -9,11 +9,12 @@
 use serde::{Deserialize, Serialize};
 
 use application::{
-    AgentTicketState, AppError, CreateProjectInput, CreateProjectOutput, GitGraphOutput,
-    HealthInput, HealthReport, LayoutKind, ListProjectsOutput, LiveSessionKind, OpenProjectOutput,
+    AgentTicketState, AppError, ConversationPreviewStatus, ConversationTurnWorkPreview,
+    ConversationWorkSummary, CreateProjectInput, CreateProjectOutput, GitGraphOutput, HealthInput,
+    HealthReport, LayoutKind, ListProjectsOutput, LiveSessionKind, OpenProjectOutput,
     ProjectWorkState, TicketWorkSource, TicketWorkStatus,
 };
-use domain::{AgentBusyState, Project, ProjectId};
+use domain::{AgentBusyState, Project, ProjectId, TurnRole};
 
 /// Request DTO for the `health` command.
 #[derive(Debug, Clone, Default, Deserialize)]
@@ -1603,12 +1604,106 @@ pub struct AgentWorkStateDto {
     pub tickets: Vec<AgentTicketStateDto>,
 }
 
+/// How much of a [`ConversationWorkSummaryDto`] could be derived, best-effort.
+#[derive(Debug, Clone, Copy, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum ConversationPreviewStatusDto {
+    /// A handoff was present and usable.
+    Ready,
+    /// No handoff yet; `recentTurns` may carry the log fallback.
+    Missing,
+    /// The handoff was unreadable but the log fallback was readable.
+    Partial,
+    /// Neither the handoff nor the log could be read.
+    Unavailable,
+}
+
+impl From<ConversationPreviewStatus> for ConversationPreviewStatusDto {
+    fn from(status: ConversationPreviewStatus) -> Self {
+        match status {
+            ConversationPreviewStatus::Ready => Self::Ready,
+            ConversationPreviewStatus::Missing => Self::Missing,
+            ConversationPreviewStatus::Partial => Self::Partial,
+            ConversationPreviewStatus::Unavailable => Self::Unavailable,
+        }
+    }
+}
+
+/// One recent turn surfaced in a conversation summary's log fallback.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ConversationTurnWorkPreviewDto {
+    /// Nature of the turn (`prompt`/`response`/`toolActivity`).
+    pub role: TurnRole,
+    /// Origin of the turn (human operator or a delegating agent).
+    pub source: TicketWorkSourceDto,
+    /// Timestamp (epoch milliseconds) of the turn.
+    pub at_ms: u64,
+    /// Bounded excerpt of the turn text.
+    pub text_preview: String,
+    /// Character length of the original (un-truncated) turn text.
+    pub text_len: usize,
+}
+
+impl From<ConversationTurnWorkPreview> for ConversationTurnWorkPreviewDto {
+    fn from(turn: ConversationTurnWorkPreview) -> Self {
+        Self {
+            role: turn.role,
+            source: turn.source.into(),
+            at_ms: turn.at_ms,
+            text_preview: turn.text_preview,
+            text_len: turn.text_len,
+        }
+    }
+}
+
+/// Best-effort, read-only summary of one conversation visible through the tickets.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ConversationWorkSummaryDto {
+    /// The conversation (pair) this summary describes.
+    pub conversation_id: String,
+    /// How much could be derived.
+    pub status: ConversationPreviewStatusDto,
+    /// Bounded excerpt of the handoff objective, when present.
+    pub objective_preview: Option<String>,
+    /// Bounded excerpt of the handoff summary, when present.
+    pub summary_preview: Option<String>,
+    /// Character length of the original (un-truncated) handoff summary (`0` when none).
+    pub summary_len: usize,
+    /// Cursor (last turn id) covered by the handoff summary, when present.
+    pub up_to: Option<String>,
+    /// Bounded, recent turns from the log fallback.
+    pub recent_turns: Vec<ConversationTurnWorkPreviewDto>,
+}
+
+impl From<ConversationWorkSummary> for ConversationWorkSummaryDto {
+    fn from(summary: ConversationWorkSummary) -> Self {
+        Self {
+            conversation_id: summary.conversation_id.to_string(),
+            status: summary.status.into(),
+            objective_preview: summary.objective_preview,
+            summary_preview: summary.summary_preview,
+            summary_len: summary.summary_len,
+            up_to: summary.up_to.map(|cursor| cursor.to_string()),
+            recent_turns: summary
+                .recent_turns
+                .into_iter()
+                .map(ConversationTurnWorkPreviewDto::from)
+                .collect(),
+        }
+    }
+}
+
 /// Project-level read model for conversation/delegation UX.
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ProjectWorkStateDto {
     /// Manifest agents in manifest order, enriched with live/busy state.
     pub agents: Vec<AgentWorkStateDto>,
+    /// Best-effort summaries of the conversations referenced by the tickets,
+    /// joined frontend-side via `tickets[].conversationId`.
+    pub conversations: Vec<ConversationWorkSummaryDto>,
 }
 
 impl From<ProjectWorkState> for ProjectWorkStateDto {
@@ -1634,6 +1729,11 @@ impl From<ProjectWorkState> for ProjectWorkStateDto {
                         .collect(),
                 })
                 .collect(),
+            conversations: state
+                .conversations
+                .into_iter()
+                .map(ConversationWorkSummaryDto::from)
+                .collect(),
         }
     }
 }