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/core/Cargo.toml

@@ -90,6 +90,7 @@ tokio = { workspace = true, features = [
     "signal",
 ] }
 tokio-util = { workspace = true, features = ["rt"] }
+tokio-tungstenite = { workspace = true }
 toml = { workspace = true }
 toml_edit = { workspace = true }
 tracing = { workspace = true, features = ["log"] }
@@ -145,6 +146,10 @@ image = { workspace = true, features = ["jpeg", "png"] }
 maplit = { workspace = true }
 predicates = { workspace = true }
 pretty_assertions = { workspace = true }
+opentelemetry_sdk = { workspace = true, features = [
+    "experimental_metrics_custom_reader",
+    "metrics",
+] }
 serial_test = { workspace = true }
 tempfile = { workspace = true }
 tracing-subscriber = { workspace = true }