fix: restore yaml import and async job result contracts

crates/crank-core/src/agent.rs

@@ -26,7 +26,7 @@ pub struct Agent {
     pub created_at: OffsetDateTime,
     #[serde(with = "time::serde::rfc3339")]
     pub updated_at: OffsetDateTime,
-    #[serde(with = "time::serde::rfc3339::option")]
+    #[serde(default, with = "time::serde::rfc3339::option")]
     pub published_at: Option<OffsetDateTime>,
 }
 

crates/crank-core/src/operation.rs

@@ -236,7 +236,7 @@ pub struct Operation<TSchema, TMapping> {
     pub created_at: OffsetDateTime,
     #[serde(with = "time::serde::rfc3339")]
     pub updated_at: OffsetDateTime,
-    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     #[serde(with = "time::serde::rfc3339::option")]
     pub published_at: Option<OffsetDateTime>,
 }
@@ -517,4 +517,46 @@ mod tests {
         assert!(yaml.contains("export_mode: portable"));
         assert_eq!(restored, operation);
     }
+
+    #[test]
+    fn operation_yaml_deserializes_without_optional_published_at() {
+        let yaml = r#"
+id: op_01
+name: crm_create_lead
+display_name: Create Lead
+category: sales
+protocol: rest
+status: draft
+version: 1
+target:
+  kind: rest
+  base_url: https://api.example.com
+  method: POST
+  path_template: /v1/leads
+  static_headers: {}
+input_schema:
+  type: object
+output_schema:
+  type: object
+input_mapping:
+  rules: []
+output_mapping:
+  rules: []
+execution_config:
+  timeout_ms: 10000
+  headers: {}
+tool_description:
+  title: Create CRM lead
+  description: Creates a new lead.
+  tags: []
+  examples: []
+created_at: 2026-03-25T08:00:00Z
+updated_at: 2026-03-25T08:10:00Z
+"#;
+
+        let restored: Operation<serde_json::Value, serde_json::Value> =
+            serde_yaml::from_str(yaml).unwrap();
+
+        assert_eq!(restored.published_at, None);
+    }
 }