feat: implémentation et QA ticket99 - agent model configuration v2

- backend A-C: VO Codex/Claude, renderers/projecteurs modèle, SecretRef/env, catalogues/use cases/Tauri commands
- frontend D: profils Codex/Claude provider->model->secret, validations, conservation SecretRef
- fix: app-tauri embedded_server isolant IDEA_WEB_ROOT

QA: backend 57/57 tests, frontend 74/74 tests OK

.ideai/tickets/index.json

@@ -1025,11 +1025,11 @@
       "issueRef": "#99",
       "path": "99",
       "title": "Modèle par agent contrôlable pour Codex & Claude (headless + TUI) — égaler le pattern OpenCode",
-      "status": "open",
+      "status": "qa",
       "priority": "high",
       "sprint": null,
       "assignedAgentIds": [],
-      "updatedAt": 1784987973464
+      "updatedAt": 1785059758742
     },
     {
       "issueRef": "#100",