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/app-server-protocol/src/protocol/v2/config.rs

@@ -787,6 +787,9 @@ pub struct ExternalAgentConfigImportItemTypeSuccess {
     pub cwd: Option<PathBuf>,
     pub source: Option<String>,
     pub target: Option<String>,
+    /// Original title for an imported session; null for other item types.
+    #[serde(default)]
+    pub title: Option<String>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
@@ -798,6 +801,29 @@ pub struct ExternalAgentConfigImportTypeResult {
     pub failures: Vec<ExternalAgentConfigImportItemTypeFailure>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExternalAgentConfigImportHistoryRecordSuccessParams {
+    pub item_type: ExternalAgentConfigMigrationItemType,
+    pub cwd: Option<PathBuf>,
+    pub source: Option<String>,
+    pub target: Option<String>,
+    /// Original title for an imported session, when available.
+    #[serde(default)]
+    #[ts(optional = nullable)]
+    pub title: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExternalAgentConfigImportHistoryRecordTypeResultParams {
+    pub item_type: ExternalAgentConfigMigrationItemType,
+    pub successes: Vec<ExternalAgentConfigImportHistoryRecordSuccessParams>,
+    pub failures: Vec<ExternalAgentConfigImportItemTypeFailure>,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]
@@ -805,7 +831,7 @@ pub struct ExternalAgentConfigImportHistoryRecordParams {
     /// Opaque provider identifier for the externally completed import.
     pub provider_id: String,
     /// Completed results grouped by imported item type.
-    pub item_type_results: Vec<ExternalAgentConfigImportTypeResult>,
+    pub item_type_results: Vec<ExternalAgentConfigImportHistoryRecordTypeResultParams>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]