fix(app-server): set originator header from initialize (re-revert) (#8988)

Reapplies https://github.com/openai/codex/pull/8873 which was reverted
due to merge conflicts

codex-rs/core/src/otel_init.rs

@@ -15,6 +15,7 @@ use std::error::Error;
 pub fn build_provider(
     config: &Config,
     service_version: &str,
+    service_name_override: Option<&str>,
     default_analytics_enabled: bool,
 ) -> Result<Option<OtelProvider>, Box<dyn Error>> {
     let to_otel_exporter = |kind: &Kind| match kind {
@@ -74,8 +75,11 @@ pub fn build_provider(
         OtelExporter::None
     };
 
+    let originator = originator();
+    let service_name = service_name_override.unwrap_or(originator.value.as_str());
+
     OtelProvider::from(&OtelSettings {
-        service_name: originator().value.to_owned(),
+        service_name: service_name.to_string(),
         service_version: service_version.to_string(),
         codex_home: config.codex_home.clone(),
         environment: config.otel.environment.to_string(),