restore .ideai/tickets/ store versionnέ + corrige .gitignore

- Restaure .ideai/tickets/ depuis 851f1f8^ (167 tickets + index.json + counter.json)
- Enlève les ignore rules .ideai/tickets/ dans .gitignore (ligne 51 et 75)
- Permet le suivi durable du store tickets futur
- Ne touche pas sdk/ (reste untracked)

.ideai/tickets/6/carnet.md

@@ -0,0 +1,6 @@
+---
+issueRef: "#6"
+version: 15
+updatedBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
+updatedAt: 1783312054217
+---

.ideai/tickets/6/issue.md

@@ -0,0 +1,15 @@
+---
+id: "b9ec818e-918e-489a-983c-04c62757bf53"
+number: 6
+title: "Suppression d'un ticket"
+status: "closed"
+priority: "low"
+links: []
+agentRefs: [{"agentId":"a6ced819-b893-4213-b003-9e9dc79b9641","role":"assigned"}]
+createdBy: {"kind":"user"}
+updatedBy: {"kind":"agent","agent_id":"a6ced819-b893-4213-b003-9e9dc79b9641"}
+createdAt: 1783166803287
+updatedAt: 1783312054217
+version: 15
+---
+Un ticket doit pouvoir être supprimé