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/ports/index.ts

@@ -34,6 +34,7 @@ import type {
   Skill,
   SkillScope,
   Template,
+  TerminalSession,
   Unsubscribe,
 } from "@/domain";
 
@@ -96,6 +97,21 @@ export interface AgentGateway {
   ): Promise<LiveAgent>;
   /** Creates a new agent from scratch; returns the created agent. */
   createAgent(projectId: string, input: CreateAgentInput): Promise<Agent>;
+  /**
+   * Hot-swaps an agent's runtime AI profile (Chantier A). The conversation
+   * history is abandoned (the product decision is "start fresh"); the agent's
+   * context `.md` and project memory are preserved. When the agent has a live
+   * session it is relaunched on the new profile and returned as
+   * {@link TerminalSession} so the hosting cell can rebind; otherwise
+   * `relaunchedSession` is absent.
+   */
+  changeAgentProfile(
+    projectId: string,
+    agentId: string,
+    profileId: string,
+    rows: number,
+    cols: number,
+  ): Promise<{ agent: Agent; relaunchedSession?: TerminalSession }>;
   /** Reads an agent's `.md` context by agent id. */
   readContext(projectId: string, agentId: string): Promise<string>;
   /** Overwrites an agent's `.md` context. */