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>

frontend/src/adapters/agent.ts

@@ -14,7 +14,7 @@
 
 import { Channel, invoke } from "@tauri-apps/api/core";
 
-import type { Agent } from "@/domain";
+import type { Agent, TerminalSession } from "@/domain";
 import type {
   AgentGateway,
   ConversationDetails,
@@ -74,6 +74,23 @@ export class TauriAgentGateway implements AgentGateway {
     });
   }
 
+  changeAgentProfile(
+    projectId: string,
+    agentId: string,
+    profileId: string,
+    rows: number,
+    cols: number,
+  ): Promise<{ agent: Agent; relaunchedSession?: TerminalSession }> {
+    // `change_agent_profile` takes a single `request` DTO; the camelCase keys
+    // match the backend `ChangeAgentProfileRequestDto`. The response carries the
+    // mutated agent and, when a live session was hot-swapped, the relaunched one
+    // (omitted otherwise — `relaunchedSession` stays `undefined`).
+    return invoke<{ agent: Agent; relaunchedSession?: TerminalSession }>(
+      "change_agent_profile",
+      { request: { projectId, agentId, profileId, rows, cols } },
+    );
+  }
+
   readContext(projectId: string, agentId: string): Promise<string> {
     return invoke<string>("read_agent_context", { projectId, agentId });
   }