Require prefixes for outbound response item IDs (#32312)

## What changed

- Add a `ResponseItemId` type that generates item-specific prefixes with UUIDv7 suffixes and use it across response items.
- Keep deserialization permissive for legacy histories, but omit empty or unprefixed item IDs from HTTP and WebSocket requests.
- Export the new type in the generated TypeScript protocol schema.

## Testing

- Cover prefixed ID generation, legacy deserialization, prefix recognition, and outbound request filtering.

GitOrigin-RevId: 0209fe430c826d0ae88bc4648652c4ebf390c4a4

codex-rs/core/src/client_tests.rs

@@ -414,7 +414,7 @@ fn started_inference_attempt(temp: &TempDir) -> anyhow::Result<InferenceTraceAtt
 
 fn output_message(id: &str, text: &str) -> ResponseItem {
     ResponseItem::Message {
-        id: Some(id.to_string()),
+        id: Some(codex_protocol::ResponseItemId::with_suffix("msg", id)),
         role: "assistant".to_string(),
         content: vec![ContentItem::OutputText {
             text: text.to_string(),
@@ -581,7 +581,7 @@ async fn dropped_response_stream_traces_cancelled_partial_output() -> anyhow::Re
     // response.completed event. The harness has enough information to keep this
     // item in history, so the trace should preserve it when the stream is
     // abandoned.
-    let item = output_message("msg-1", "partial answer");
+    let item = output_message("1", "partial answer");
     let api_stream = futures::stream::iter([Ok(ResponseEvent::OutputItemDone(item))])
         .chain(futures::stream::pending());
     let (mut stream, _) = super::map_response_events(
@@ -699,7 +699,7 @@ async fn dropped_backpressured_response_stream_traces_cancelled_partial_output()
         events.push_back(ResponseEvent::Created);
     }
     events.push_back(ResponseEvent::OutputItemDone(output_message(
-        "msg-1",
+        "1",
         "partial answer",
     )));
     let api_stream = NotifyAfterEventStream {