[codex] Forward turn moderation metadata through app-server (#25710)

## Why
First-party backends can supply turn-scoped moderation metadata that
app-server clients need for client-side presentation. Exposing this as
an experimental typed notification lets opted-in clients consume it
without interpreting raw Responses API events.

## What changed
- forward `response.metadata.openai_chatgpt_moderation_metadata` from
Responses API SSE and WebSocket streams as turn-scoped moderation
metadata
- emit the experimental app-server v2 `turn/moderationMetadata`
notification with `{ threadId, turnId, metadata }`
- add app-server integration coverage for the typed moderation metadata
notification

## Testing
- `just test -p codex-core
build_ws_client_metadata_includes_window_lineage_and_turn_metadata`
- `just test -p codex-core` (fails locally: 46 failures and 1 timeout,
primarily missing `test_stdio_server` and shell snapshot timeouts)
- `just test -p codex-app-server-protocol`
- `just test -p codex-app-server
turn_moderation_metadata_emits_typed_notification_v2`
- `just test -p codex-app-server` (fails locally: 792 passed, 10 failed,
and 5 timed out; failures are in existing environment-sensitive tests,
primarily because nested macOS `sandbox-exec` is not permitted)
- `just write-app-server-schema --experimental --schema-root
/tmp/codex-app-server-schema-experimental`

codex-rs/rollout-trace/src/protocol_event.rs

@@ -224,6 +224,7 @@ pub(crate) fn tool_runtime_trace_event(event: &EventMsg) -> Option<ToolRuntimeTr
         | EventMsg::RealtimeConversationSdp(_)
         | EventMsg::ModelReroute(_)
         | EventMsg::ModelVerification(_)
+        | EventMsg::TurnModerationMetadata(_)
         | EventMsg::ContextCompacted(_)
         | EventMsg::ThreadRolledBack(_)
         | EventMsg::ThreadGoalUpdated(_)
@@ -297,6 +298,7 @@ pub(crate) fn wrapped_protocol_event_type(event: &EventMsg) -> Option<&'static s
         | EventMsg::RealtimeConversationSdp(_)
         | EventMsg::ModelReroute(_)
         | EventMsg::ModelVerification(_)
+        | EventMsg::TurnModerationMetadata(_)
         | EventMsg::ContextCompacted(_)
         | EventMsg::ThreadSettingsApplied(_)
         | EventMsg::TokenCount(_)