Track image generation request IDs in analytics (#40714)

## What changed

- Read `x-codex-imagegen-request-id` from image generation and edit responses.
- Propagate the ID to `codex_image_generation_event` analytics.
- Keep the ID in process only, excluding it from extension item serialization, generated types, app-server wire data, and rollout history.

## Testing

- Cover response-header extraction and missing-header behavior in the images client.
- Verify end-to-end analytics emission and the unchanged image-generation item wire shape.

GitOrigin-RevId: 9b8e09b7d655c0c2faa84f0eee99aabae583668d

codex-rs/app-server/tests/suite/v2/imagegen_extension.rs

@@ -34,6 +34,9 @@ use wiremock::ResponseTemplate;
 use wiremock::matchers::method;
 use wiremock::matchers::path;
 
+use super::analytics::mount_analytics_capture;
+use super::analytics::wait_for_analytics_event;
+
 const RESULT: &str = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR4nGP4z8DwHwAFAAH/iZk9HQAAAABJRU5ErkJggg==";
 const TINY_PNG_BYTES: &[u8] = &[
     137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 1, 0, 0, 0, 1, 8, 6, 0,
@@ -87,11 +90,7 @@ async fn standalone_image_generation_returns_saved_path_hint_to_model() -> Resul
 
     let codex_home = TempDir::new()?;
     create_config_toml(codex_home.path(), &server.uri(), ImagegenTestMode::Direct)?;
-    write_chatgpt_auth(
-        codex_home.path(),
-        ChatGptAuthFixture::new("access-chatgpt"),
-        AuthCredentialsStoreMode::File,
-    )?;
+    mount_analytics_capture(&server, codex_home.path()).await?;
 
     let mut mcp = TestAppServer::builder()
         .with_codex_home(codex_home.path())
@@ -183,6 +182,17 @@ async fn standalone_image_generation_returns_saved_path_hint_to_model() -> Resul
         "standalone image generation should not emit the legacy developer-message hint"
     );
 
+    let event = wait_for_analytics_event(
+        &server,
+        DEFAULT_READ_TIMEOUT,
+        "codex_image_generation_event",
+    )
+    .await?;
+    assert_eq!(
+        event["event_params"]["imagegen_request_id"],
+        json!("req-imagegen-123")
+    );
+
     Ok(())
 }
 
@@ -419,6 +429,7 @@ async fn standalone_image_generation_failure_emits_terminal_item() -> Result<()>
             transparent_background: None,
             failure: None,
             saved_path: None,
+            imagegen_request_id: None,
         })
     );
 
@@ -922,11 +933,15 @@ async fn mount_image_response(server: &MockServer) {
 async fn mount_image_response_with_background(server: &MockServer, background: &str) {
     Mock::given(method("POST"))
         .and(path("/api/codex/images/generations"))
-        .respond_with(ResponseTemplate::new(200).set_body_json(json!({
-            "created": 1,
-            "background": background,
-            "data": [{"b64_json": RESULT}],
-        })))
+        .respond_with(
+            ResponseTemplate::new(200)
+                .insert_header("x-codex-imagegen-request-id", "req-imagegen-123")
+                .set_body_json(json!({
+                    "created": 1,
+                    "background": background,
+                    "data": [{"b64_json": RESULT}],
+                })),
+        )
         .expect(1)
         .mount(server)
         .await;