feat(chat): persistance bornee du brouillon custom chat par projet/layout (#182)

crates/domain/tests/chat_draft.rs

@@ -0,0 +1,26 @@
+use domain::{ChatDraft, ChatDraftError, ChatDraftKey, LayoutId, NodeId, ProjectId};
+use uuid::Uuid;
+
+fn key() -> ChatDraftKey {
+    ChatDraftKey::new(
+        ProjectId::from_uuid(Uuid::from_u128(1)),
+        LayoutId::from_uuid(Uuid::from_u128(2)),
+        NodeId::from_uuid(Uuid::from_u128(3)),
+    )
+}
+
+#[test]
+fn chat_draft_accepts_text_and_scope() {
+    let draft = ChatDraft::new(key(), "hello", 42).unwrap();
+
+    assert_eq!(draft.key, key());
+    assert_eq!(draft.text, "hello");
+    assert_eq!(draft.updated_at_ms, 42);
+}
+
+#[test]
+fn chat_draft_rejects_oversized_text() {
+    let err = ChatDraft::new(key(), "x".repeat(domain::CHAT_DRAFT_MAX_BYTES + 1), 42).unwrap_err();
+
+    assert!(matches!(err, ChatDraftError::TooLarge { .. }));
+}