Include session titles in external agent import history (#35870)

## What changed

- Preserve the original title when importing an external-agent session and return it with successful session entries from `externalAgentConfig/import/readHistories`.
- Add dedicated history-record success types so externally completed imports can optionally supply a session title without changing the live import result type.

## Testing

- Verify imported session titles are returned by the app server and persisted when session import ledger entries are created or refreshed.

GitOrigin-RevId: e896688a5763c238f1e1dc8b4672a7aa7bc1ed4c

codex-rs/external-agent-migration/src/sessions/ledger.rs

@@ -31,6 +31,8 @@ struct ImportedExternalAgentSessionRecord {
     source_modified_at: Option<i64>,
     #[serde(default)]
     connector_names: Vec<String>,
+    #[serde(default)]
+    title: Option<String>,
 }
 
 #[derive(Debug, PartialEq, Eq)]
@@ -39,6 +41,7 @@ pub struct CompletedExternalAgentSessionImport {
     pub source_content_sha256: String,
     pub imported_thread_id: ThreadId,
     pub connector_names: Vec<String>,
+    pub title: Option<String>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -74,6 +77,7 @@ pub(crate) fn record_imported_session(
             source_path,
             imported_thread_id,
             connector_names: Vec::new(),
+            title: None,
         }],
     )
 }
@@ -98,6 +102,7 @@ pub fn record_completed_session_imports(
             record.imported_at = imported_at;
             record.source_modified_at = source_modified_at.or(record.source_modified_at);
             record.connector_names = import.connector_names;
+            record.title = import.title;
             ledger.records.push(record);
             continue;
         }
@@ -108,6 +113,7 @@ pub fn record_completed_session_imports(
             imported_at,
             source_modified_at,
             connector_names: import.connector_names,
+            title: import.title,
         });
     }
     save_import_ledger(codex_home, &ledger)

codex-rs/external-agent-migration/src/sessions/ledger_tests.rs

@@ -38,6 +38,7 @@ fn completed_imports_do_not_read_source_files() {
             source_content_sha256: format!("{:x}", Sha256::digest(contents)),
             imported_thread_id,
             connector_names: Vec::new(),
+            title: Some("Imported session".to_string()),
         }],
     )
     .expect("record completed imports");
@@ -47,6 +48,7 @@ fn completed_imports_do_not_read_source_files() {
     assert_eq!(ledger.records[0].source_path, source_path);
     assert_eq!(ledger.records[0].imported_thread_id, imported_thread_id);
     assert_eq!(ledger.records[0].source_modified_at, None);
+    assert_eq!(ledger.records[0].title.as_deref(), Some("Imported session"));
 }
 
 #[test]
@@ -68,6 +70,7 @@ fn completed_import_refreshes_existing_record_metadata() {
             source_content_sha256: content_sha256.clone(),
             imported_thread_id: first_thread_id,
             connector_names: vec!["Gmail".to_string()],
+            title: Some("First title".to_string()),
         }],
     )
     .expect("record first import");
@@ -78,6 +81,7 @@ fn completed_import_refreshes_existing_record_metadata() {
             source_content_sha256: content_sha256,
             imported_thread_id: second_thread_id,
             connector_names: vec!["Slack".to_string()],
+            title: Some("Second title".to_string()),
         }],
     )
     .expect("record replacement import");
@@ -88,6 +92,7 @@ fn completed_import_refreshes_existing_record_metadata() {
     assert_eq!(ledger.records[0].imported_thread_id, second_thread_id);
     assert!(ledger.records[0].source_modified_at.is_some());
     assert_eq!(ledger.records[0].connector_names, vec!["Slack"]);
+    assert_eq!(ledger.records[0].title.as_deref(), Some("Second title"));
 }
 
 #[test]
@@ -105,18 +110,21 @@ fn connector_candidates_use_latest_import_for_each_source() {
                 source_content_sha256: "first-version".to_string(),
                 imported_thread_id: ThreadId::new(),
                 connector_names: vec!["Gmail".to_string()],
+                title: None,
             },
             CompletedExternalAgentSessionImport {
                 source_path: first_source,
                 source_content_sha256: "second-version".to_string(),
                 imported_thread_id: ThreadId::new(),
                 connector_names: vec!["Slack".to_string()],
+                title: None,
             },
             CompletedExternalAgentSessionImport {
                 source_path: second_source,
                 source_content_sha256: "only-version".to_string(),
                 imported_thread_id: ThreadId::new(),
                 connector_names: vec!["Gmail".to_string(), "Slack".to_string()],
+                title: None,
             },
         ],
     )