Forward thread originators from standalone extensions (#33677)

## Why

Standalone web search and image requests need to preserve the trusted,
thread-scoped originator used for billing attribution.

## What changed

- Seed extension data with the resolved thread originator and recognize
  `codex_work_cca` and `chatgpt_cca` service names as originators.
- Forward non-default originators from the web search and image generation
  extensions with the shared originator-header helper.

## Testing

- Cover originator resolution, header validation, and forwarding for web
  search, image generation, and image editing.

GitOrigin-RevId: 165dace8e4d24e4bd92f234bff5ec77a21a7ff6e

codex-rs/ext/image-generation/src/backend.rs

@@ -3,6 +3,7 @@ use codex_api::ImageGenerationRequest;
 use codex_api::ImageResponse;
 use codex_api::ImagesClient;
 use codex_api::ReqwestTransport;
+use codex_login::default_client::add_originator_header;
 use codex_login::default_client::build_reqwest_client;
 use codex_model_provider::SharedModelProvider;
 use http::HeaderMap;
@@ -10,12 +11,16 @@ use http::HeaderMap;
 #[derive(Clone)]
 pub(crate) struct CodexImagesBackend {
     provider: SharedModelProvider,
+    originator: Option<String>,
 }
 
 impl CodexImagesBackend {
     /// Creates a backend that sends image requests through the active model provider.
-    pub(crate) fn new(provider: SharedModelProvider) -> Self {
-        Self { provider }
+    pub(crate) fn new(provider: SharedModelProvider, originator: Option<String>) -> Self {
+        Self {
+            provider,
+            originator,
+        }
     }
 
     /// Resolves the provider and auth required for the current image API request.
@@ -44,7 +49,7 @@ impl CodexImagesBackend {
     ) -> Result<ImageResponse, String> {
         self.client()
             .await?
-            .generate(&request, HeaderMap::new())
+            .generate(&request, image_request_headers(self.originator.as_deref()))
             .await
             .map_err(|err| err.to_string())
     }
@@ -53,8 +58,16 @@ impl CodexImagesBackend {
     pub(crate) async fn edit(&self, request: ImageEditRequest) -> Result<ImageResponse, String> {
         self.client()
             .await?
-            .edit(&request, HeaderMap::new())
+            .edit(&request, image_request_headers(self.originator.as_deref()))
             .await
             .map_err(|err| err.to_string())
     }
 }
+
+fn image_request_headers(originator: Option<&str>) -> HeaderMap {
+    let mut headers = HeaderMap::new();
+    if let Some(originator) = originator {
+        add_originator_header(&mut headers, originator);
+    }
+    headers
+}