Add websocket telemetry metrics and labels (#10316)

Summary
- expose websocket telemetry hooks through the responses client so
request durations and event processing can be reported
- record websocket request/event metrics and emit runtime telemetry
events that the history UI now surfaces
- improve tests to cover websocket telemetry reporting and guard runtime
summary updates


<img width="824" height="79" alt="Screenshot 2026-01-31 at 5 28 12 PM"
src="https://github.com/user-attachments/assets/ea9a7965-d8b4-4e3c-a984-ef4fdc44c81d"
/>

codex-rs/codex-api/src/sse/responses.rs

@@ -157,7 +157,7 @@ struct ResponseCompletedOutputTokensDetails {
 #[derive(Deserialize, Debug)]
 pub struct ResponsesStreamEvent {
     #[serde(rename = "type")]
-    kind: String,
+    pub(crate) kind: String,
     response: Option<Value>,
     item: Option<Value>,
     delta: Option<String>,