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/src/dto.rs

@@ -1032,10 +1032,10 @@ pub fn parse_profile_id(raw: &str) -> Result<ProfileId, ErrorDto> {
 // ---------------------------------------------------------------------------
 
 use application::{
-    CreateAgentOutput, InspectConversationOutput, LaunchAgentOutput, ListAgentsOutput,
-    ReadAgentContextOutput,
+    ChangeAgentProfileOutput, CreateAgentOutput, InspectConversationOutput, LaunchAgentOutput,
+    ListAgentsOutput, ReadAgentContextOutput,
 };
-use domain::Agent;
+use domain::{Agent, TerminalSession};
 
 /// An agent crossing the wire. [`Agent`] already serialises camelCase
 /// (`id`, `name`, `contextPath`, `profileId`, `origin` tagged, `synchronized`),
@@ -1154,6 +1154,56 @@ impl From<LaunchAgentOutput> for TerminalSessionDto {
     }
 }
 
+/// Request DTO for `change_agent_profile` (§15.1): hot-swap an agent's runtime
+/// profile, optionally relaunching its live session in place.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ChangeAgentProfileRequestDto {
+    /// Id of the owning project.
+    pub project_id: String,
+    /// Id of the agent whose runtime profile to change.
+    pub agent_id: String,
+    /// Id of the new runtime profile.
+    pub profile_id: String,
+    /// Terminal height in rows for a possible hot relaunch.
+    pub rows: u16,
+    /// Terminal width in columns for a possible hot relaunch.
+    pub cols: u16,
+}
+
+/// Response DTO for `change_agent_profile`: the mutated agent plus the freshly
+/// relaunched session when a live session was hot-swapped (absent otherwise).
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ChangeAgentProfileDto {
+    /// The agent now carrying the new profile.
+    pub agent: AgentDto,
+    /// The relaunched session, present only when a live session was swapped.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub relaunched_session: Option<TerminalSessionDto>,
+}
+
+impl From<ChangeAgentProfileOutput> for ChangeAgentProfileDto {
+    fn from(out: ChangeAgentProfileOutput) -> Self {
+        Self {
+            agent: AgentDto(out.agent),
+            relaunched_session: out.relaunched.map(TerminalSessionDto::from),
+        }
+    }
+}
+
+impl From<TerminalSession> for TerminalSessionDto {
+    fn from(s: TerminalSession) -> Self {
+        Self {
+            session_id: s.id.to_string(),
+            cwd: s.cwd.as_str().to_owned(),
+            rows: s.pty_size.rows,
+            cols: s.pty_size.cols,
+            assigned_conversation_id: None,
+        }
+    }
+}
+
 /// Request DTO for `inspect_conversation` (T7).
 #[derive(Debug, Clone, Deserialize)]
 #[serde(rename_all = "camelCase")]