feat(agent): UI hot-swap de profil (A2) — commande Tauri + sélecteur + dialog

- Tauri : commande change_agent_profile + ChangeAgentProfileRequestDto/Dto
  (camelCase, relaunchedSession omis si None), câblage state.rs par composition.
- Front : gateway changeAgentProfile (adapters Tauri+mock), sélecteur de profil
  par agent, dialog de confirmation FR (« Changer le moteur abandonne l'historique
  de conversation… »), refresh sur event agentProfileChanged.

Tests : app-tauri dto 5/5 ; vitest 314/314 (mapping, payload, dialog gating,
libellé FR, refresh). 0 régression.

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

crates/app-tauri/tests/dto_change_agent_profile.rs

@@ -0,0 +1,155 @@
+//! A2 tests for the `change_agent_profile` DTO contract (§15.1):
+//! - Request DTO round-trips camelCase JSON `{ projectId, agentId, profileId, rows, cols }`.
+//! - `From<ChangeAgentProfileOutput> for ChangeAgentProfileDto` maps the agent and
+//!   surfaces `relaunchedSession` only when a live session was swapped (omitted via
+//!   `skip_serializing_if` when `None`).
+//! - `From<TerminalSession> for TerminalSessionDto` carries id/cwd/size.
+
+use app_tauri_lib::dto::{ChangeAgentProfileDto, ChangeAgentProfileRequestDto};
+use application::ChangeAgentProfileOutput;
+use domain::ids::{AgentId, NodeId, ProfileId, SessionId};
+use domain::terminal::{PtySize, SessionKind, SessionStatus, TerminalSession};
+use domain::{Agent, AgentOrigin, ProjectPath};
+use serde_json::json;
+use uuid::Uuid;
+
+/// Helper: build a minimal validated [`Agent`].
+fn make_agent(agent_uuid: u128, profile_uuid: u128) -> Agent {
+    Agent::new(
+        AgentId::from_uuid(Uuid::from_u128(agent_uuid)),
+        "My Agent",
+        "agents/my-agent.md",
+        ProfileId::from_uuid(Uuid::from_u128(profile_uuid)),
+        AgentOrigin::Scratch,
+        false,
+    )
+    .expect("valid agent")
+}
+
+/// Helper: build a running [`TerminalSession`] for an agent cell.
+fn make_session(session_uuid: u128, node_uuid: u128, agent_uuid: u128) -> TerminalSession {
+    let session_id = SessionId::from_uuid(Uuid::from_u128(session_uuid));
+    let node_id = NodeId::from_uuid(Uuid::from_u128(node_uuid));
+    let agent_id = AgentId::from_uuid(Uuid::from_u128(agent_uuid));
+    let cwd = ProjectPath::new("/tmp/project".to_owned()).expect("valid path");
+    let size = PtySize::new(30, 100).unwrap();
+    let mut session = TerminalSession::starting(
+        session_id,
+        node_id,
+        cwd,
+        SessionKind::Agent { agent_id },
+        size,
+    );
+    session.status = SessionStatus::Running;
+    session
+}
+
+// ---------------------------------------------------------------------------
+// Request DTO deserialisation (camelCase round-trip)
+// ---------------------------------------------------------------------------
+
+#[test]
+fn change_agent_profile_request_deserialises_camelcase() {
+    let project_id = Uuid::from_u128(1).to_string();
+    let agent_id = Uuid::from_u128(2).to_string();
+    let profile_id = Uuid::from_u128(3).to_string();
+    let raw = json!({
+        "projectId": project_id,
+        "agentId": agent_id,
+        "profileId": profile_id,
+        "rows": 24,
+        "cols": 80
+    });
+    let dto: ChangeAgentProfileRequestDto = serde_json::from_value(raw).unwrap();
+    assert_eq!(dto.project_id, project_id);
+    assert_eq!(dto.agent_id, agent_id);
+    assert_eq!(dto.profile_id, profile_id);
+    assert_eq!(dto.rows, 24);
+    assert_eq!(dto.cols, 80);
+}
+
+#[test]
+fn change_agent_profile_request_rejects_snake_case_keys() {
+    // The wire contract is camelCase; snake_case keys must NOT satisfy the struct.
+    let raw = json!({
+        "project_id": Uuid::from_u128(1).to_string(),
+        "agent_id": Uuid::from_u128(2).to_string(),
+        "profile_id": Uuid::from_u128(3).to_string(),
+        "rows": 24,
+        "cols": 80
+    });
+    let res: Result<ChangeAgentProfileRequestDto, _> = serde_json::from_value(raw);
+    assert!(res.is_err(), "snake_case keys must not deserialise");
+}
+
+// ---------------------------------------------------------------------------
+// From<ChangeAgentProfileOutput> for ChangeAgentProfileDto
+// ---------------------------------------------------------------------------
+
+#[test]
+fn output_maps_agent_and_omits_session_when_no_relaunch() {
+    let agent = make_agent(5, 6);
+    let out = ChangeAgentProfileOutput {
+        agent: agent.clone(),
+        relaunched: None,
+    };
+    let dto = ChangeAgentProfileDto::from(out);
+    assert_eq!(dto.agent.0.id, agent.id);
+    assert!(dto.relaunched_session.is_none());
+
+    let v = serde_json::to_value(&dto).unwrap();
+    // The agent is embedded with its camelCase shape.
+    assert_eq!(v["agent"]["id"], agent.id.to_string());
+    assert_eq!(v["agent"]["profileId"], agent.profile_id.to_string());
+    // No relaunch ⇒ field must be OMITTED from the wire (absent, not null).
+    assert!(
+        v.get("relaunchedSession").is_none(),
+        "no relaunch ⇒ relaunchedSession omitted, got: {v}"
+    );
+    // No snake_case leak.
+    assert!(v.get("relaunched_session").is_none());
+}
+
+#[test]
+fn output_maps_relaunched_session_camelcase_when_present() {
+    let agent = make_agent(7, 8);
+    let session = make_session(11, 12, 7);
+    let out = ChangeAgentProfileOutput {
+        agent: agent.clone(),
+        relaunched: Some(session.clone()),
+    };
+    let dto = ChangeAgentProfileDto::from(out);
+    assert!(dto.relaunched_session.is_some());
+
+    let v = serde_json::to_value(&dto).unwrap();
+    let rs = v
+        .get("relaunchedSession")
+        .expect("relaunch present ⇒ relaunchedSession serialised");
+    assert_eq!(rs["sessionId"], session.id.to_string());
+    assert_eq!(rs["cwd"], "/tmp/project");
+    assert_eq!(rs["rows"], 30);
+    assert_eq!(rs["cols"], 100);
+    // No snake_case leak on the nested DTO.
+    assert!(rs.get("session_id").is_none(), "no snake_case leak");
+    assert!(v.get("relaunched_session").is_none());
+}
+
+// ---------------------------------------------------------------------------
+// From<TerminalSession> for TerminalSessionDto
+// ---------------------------------------------------------------------------
+
+#[test]
+fn terminal_session_maps_to_dto() {
+    let session = make_session(21, 22, 23);
+    // Exercise the From<TerminalSession> impl directly through the output mapping.
+    let out = ChangeAgentProfileOutput {
+        agent: make_agent(23, 24),
+        relaunched: Some(session.clone()),
+    };
+    let dto = ChangeAgentProfileDto::from(out);
+    let rs = dto.relaunched_session.expect("session present");
+    assert_eq!(rs.session_id, session.id.to_string());
+    assert_eq!(rs.cwd, "/tmp/project");
+    assert_eq!(rs.rows, 30);
+    assert_eq!(rs.cols, 100);
+}