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/99/issue.md

@@ -2,7 +2,7 @@
 id: "45733f3f-5ef5-4f33-96e7-25afddcd1ce6"
 number: 99
 title: "Modèle par agent contrôlable pour Codex & Claude (headless + TUI) — égaler le pattern OpenCode"
-status: "open"
+status: "qa"
 priority: "high"
 sprint: null
 links: [{"target":"#98","kind":"relatesTo"}]
@@ -10,8 +10,8 @@ agentRefs: []
 createdBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
 updatedBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
 createdAt: 1784987973464
-updatedAt: 1784987973464
-version: 1
+updatedAt: 1785059758742
+version: 3
 ---
 ## Problème