feat(workstate): actions contrôlées sur le work-state (Lot D backend)

Ajoute un module d'actions contrôlées (`workstate/actions.rs`) côté application
et l'expose via des commandes Tauri : DTO camelCase, câblage commands/state/lib.
Les actions valident leurs invariants avant d'agir sur le read-model.

- application : use cases d'actions contrôlées + intégration au work-state.
- app-tauri : commandes dédiées, DTO et enregistrement dans le handler.

Tests verts : application workstate_actions (7), workstate (21),
app-tauri dto_agents (25), list_live_agents_r0b (5), cargo check OK.

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

crates/app-tauri/src/dto.rs

@@ -9,10 +9,10 @@
 use serde::{Deserialize, Serialize};
 
 use application::{
-    AgentTicketState, AppError, ConversationPreviewStatus, ConversationTurnWorkPreview,
-    ConversationWorkSummary, CreateProjectInput, CreateProjectOutput, GitGraphOutput, HealthInput,
-    HealthReport, LayoutKind, ListProjectsOutput, LiveSessionKind, OpenProjectOutput,
-    ProjectWorkState, TicketWorkSource, TicketWorkStatus,
+    AgentTicketState, AppError, AttachLiveAgentOutput, ConversationPreviewStatus,
+    ConversationTurnWorkPreview, ConversationWorkSummary, CreateProjectInput, CreateProjectOutput,
+    GitGraphOutput, HealthInput, HealthReport, LayoutKind, ListProjectsOutput, LiveSessionKind,
+    OpenProjectOutput, ProjectWorkState, StopLiveAgentOutput, TicketWorkSource, TicketWorkStatus,
 };
 use domain::{AgentBusyState, Project, ProjectId, TurnRole};
 
@@ -1751,6 +1751,64 @@ pub struct AttachLiveAgentRequestDto {
     pub node_id: String,
 }
 
+/// Response DTO for `attach_live_agent`: the rebound live session's coordinates.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct AttachLiveAgentResponseDto {
+    /// The rebound agent's id.
+    pub agent_id: String,
+    /// The node now hosting the session view.
+    pub node_id: String,
+    /// The (unchanged) live session id.
+    pub session_id: String,
+    /// Runtime family that owns the session (`pty`/`structured`).
+    pub kind: LiveWorkSessionKindDto,
+}
+
+impl From<AttachLiveAgentOutput> for AttachLiveAgentResponseDto {
+    fn from(out: AttachLiveAgentOutput) -> Self {
+        Self {
+            agent_id: out.agent_id.to_string(),
+            node_id: out.node_id.to_string(),
+            session_id: out.session_id.to_string(),
+            kind: out.kind.into(),
+        }
+    }
+}
+
+/// Request DTO for `stop_live_agent`: tear down an already-running agent's live
+/// session by agent id (no spawn, agent entity preserved).
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct StopLiveAgentRequestDto {
+    /// Id of the owning project (validated for symmetry and future scoping).
+    pub project_id: String,
+    /// Id of the running agent to stop.
+    pub agent_id: String,
+}
+
+/// Response DTO for `stop_live_agent`: the torn-down session's coordinates.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct StopLiveAgentResponseDto {
+    /// The stopped agent's id.
+    pub agent_id: String,
+    /// The id of the session that was torn down.
+    pub session_id: String,
+    /// Runtime family that owned the session (`pty`/`structured`).
+    pub kind: LiveWorkSessionKindDto,
+}
+
+impl From<StopLiveAgentOutput> for StopLiveAgentResponseDto {
+    fn from(out: StopLiveAgentOutput) -> Self {
+        Self {
+            agent_id: out.agent_id.to_string(),
+            session_id: out.session_id.to_string(),
+            kind: out.kind.into(),
+        }
+    }
+}
+
 /// Parses an agent-id string (UUID) coming from the frontend.
 ///
 /// # Errors