docs(tickets): consigne le cycle #120 fix CORS + décision Git et états (#120)

- carnet.md: enregistre la livraison CORS et la décision Git du 2026-08-01
- issue.md + index.json: mise à jour version/timestamp
- plugins.test.tsx: tests d'intégration frontend liés
- Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.ideai/tickets/120/issue.md

@@ -9,10 +9,10 @@ links: [{"target":"#116","kind":"relatesTo"},{"target":"#43","kind":"relatesTo"}
 agentRefs: []
 attachments: []
 createdBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
-updatedBy: {"kind":"agent","agent_id":"dce19c75-9669-4e45-b8de-9950025157da"}
+updatedBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
 createdAt: 1785534496259
-updatedAt: 1785596006134
-version: 8
+updatedAt: 1785600025153
+version: 9
 ---
 ## Constat utilisateur