core: type agent timestamps

apps/mcp-server/src/main.rs

@@ -1633,8 +1633,8 @@ mod tests {
             status: AgentStatus::Draft,
             current_draft_version: 1,
             latest_published_version: None,
-            created_at: "2026-03-26T10:00:00Z".to_owned(),
-            updated_at: "2026-03-26T10:00:00Z".to_owned(),
+            created_at: OffsetDateTime::parse("2026-03-26T10:00:00Z", &Rfc3339).unwrap(),
+            updated_at: OffsetDateTime::parse("2026-03-26T10:00:00Z", &Rfc3339).unwrap(),
             published_at: None,
         };
         let version = AgentVersion {
@@ -1643,7 +1643,7 @@ mod tests {
             status: AgentStatus::Draft,
             instructions: json!({}),
             tool_selection_policy: json!({}),
-            created_at: "2026-03-26T10:00:00Z".to_owned(),
+            created_at: OffsetDateTime::parse("2026-03-26T10:00:00Z", &Rfc3339).unwrap(),
         };
 
         registry
@@ -1659,7 +1659,7 @@ mod tests {
                 workspace_id: &test_workspace_id(),
                 agent_id: &agent_id,
                 version: 1,
-                published_at: "2026-03-26T10:00:00Z",
+                published_at: &OffsetDateTime::parse("2026-03-26T10:00:00Z", &Rfc3339).unwrap(),
                 published_by: Some("alice"),
             })
             .await