protocol: separate app and exec RPC ownership (#29714)

## Why

The app-server and exec-server expose separate JSON-RPC APIs, but
exec-server currently sources its serialized protocol and envelope types
through app-server-oriented code. Giving each API an explicit owner
makes the crate boundary legible without introducing shared generic
envelopes.

## What changed

- Added `codex-exec-server-protocol` to own exec DTOs, process IDs, and
JSON-RPC envelopes.
- Updated exec-server clients, transports, handlers, and tests to use
the new crate.
- Exposed app-server's existing JSON-RPC types through a public `rpc`
module while retaining root re-exports.
- Preserved existing wire shapes, including exec `PathUri` behavior.

## Stack

This is PR 1 of 6. Next: [PR
#29721](https://github.com/openai/codex/pull/29721), which moves auth
mode below the app wire boundary.

## Validation

- Exec-server protocol and server coverage passed in the focused
protocol test runs.
- App-server protocol schema fixtures passed.

codex-rs/exec-server/src/server/file_system_handler.rs

@@ -2,7 +2,7 @@ use std::io;
 
 use base64::Engine as _;
 use base64::engine::general_purpose::STANDARD;
-use codex_app_server_protocol::JSONRPCErrorError;
+use codex_exec_server_protocol::JSONRPCErrorError;
 
 use crate::CopyOptions;
 use crate::CreateDirectoryOptions;

codex-rs/exec-server/src/server/handler.rs

@@ -3,8 +3,8 @@ use std::sync::Mutex as StdMutex;
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
 
-use codex_app_server_protocol::JSONRPCErrorError;
-use codex_app_server_protocol::RequestId;
+use codex_exec_server_protocol::JSONRPCErrorError;
+use codex_exec_server_protocol::RequestId;
 use serde_json::to_value;
 use std::collections::HashSet;
 use tokio::sync::Mutex;

codex-rs/exec-server/src/server/process_handler.rs

@@ -1,4 +1,4 @@
-use codex_app_server_protocol::JSONRPCErrorError;
+use codex_exec_server_protocol::JSONRPCErrorError;
 
 use crate::ExecServerRuntimePaths;
 use crate::local_process::LocalProcess;

codex-rs/exec-server/src/server/processor.rs

@@ -89,7 +89,7 @@ async fn run_connection(
                 warn!("ignoring malformed exec-server message: {reason}");
                 if outgoing_tx
                     .send(RpcServerOutboundMessage::Error {
-                        request_id: codex_app_server_protocol::RequestId::Integer(-1),
+                        request_id: codex_exec_server_protocol::RequestId::Integer(-1),
                         error: invalid_request(reason),
                     })
                     .await
@@ -99,7 +99,7 @@ async fn run_connection(
                 }
             }
             JsonRpcConnectionEvent::Message(message) => match message {
-                codex_app_server_protocol::JSONRPCMessage::Request(request) => {
+                codex_exec_server_protocol::JSONRPCMessage::Request(request) => {
                     if let Some(route) = router.request_route(request.method.as_str()) {
                         let message = tokio::select! {
                             message = route(Arc::clone(&handler), request) => message,
@@ -127,7 +127,7 @@ async fn run_connection(
                         break;
                     }
                 }
-                codex_app_server_protocol::JSONRPCMessage::Notification(notification) => {
+                codex_exec_server_protocol::JSONRPCMessage::Notification(notification) => {
                     let Some(route) = router.notification_route(notification.method.as_str())
                     else {
                         warn!(
@@ -150,14 +150,14 @@ async fn run_connection(
                         break;
                     }
                 }
-                codex_app_server_protocol::JSONRPCMessage::Response(response) => {
+                codex_exec_server_protocol::JSONRPCMessage::Response(response) => {
                     warn!(
                         "closing exec-server connection after unexpected client response: {:?}",
                         response.id
                     );
                     break;
                 }
-                codex_app_server_protocol::JSONRPCMessage::Error(error) => {
+                codex_exec_server_protocol::JSONRPCMessage::Error(error) => {
                     warn!(
                         "closing exec-server connection after unexpected client error: {:?}",
                         error.id
@@ -190,11 +190,11 @@ mod tests {
     use std::sync::Arc;
     use std::time::Duration;
 
-    use codex_app_server_protocol::JSONRPCMessage;
-    use codex_app_server_protocol::JSONRPCNotification;
-    use codex_app_server_protocol::JSONRPCRequest;
-    use codex_app_server_protocol::JSONRPCResponse;
-    use codex_app_server_protocol::RequestId;
+    use codex_exec_server_protocol::JSONRPCMessage;
+    use codex_exec_server_protocol::JSONRPCNotification;
+    use codex_exec_server_protocol::JSONRPCRequest;
+    use codex_exec_server_protocol::JSONRPCResponse;
+    use codex_exec_server_protocol::RequestId;
     use codex_utils_path_uri::PathUri;
     use pretty_assertions::assert_eq;
     use serde::Serialize;
@@ -382,7 +382,6 @@ mod tests {
                 id: RequestId::Integer(id),
                 method: method.to_string(),
                 params: Some(serde_json::to_value(params).expect("serialize params")),
-                trace: None,
             }),
         )
         .await;

codex-rs/exec-server/src/server/session_registry.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 use std::sync::Mutex as StdMutex;
 use std::time::Duration;
 
-use codex_app_server_protocol::JSONRPCErrorError;
+use codex_exec_server_protocol::JSONRPCErrorError;
 use tokio::sync::Mutex;
 use uuid::Uuid;
 

codex-rs/exec-server/src/server/transport_tests.rs

@@ -1,11 +1,11 @@
 use std::net::SocketAddr;
 use std::time::Duration;
 
-use codex_app_server_protocol::JSONRPCMessage;
-use codex_app_server_protocol::JSONRPCNotification;
-use codex_app_server_protocol::JSONRPCRequest;
-use codex_app_server_protocol::JSONRPCResponse;
-use codex_app_server_protocol::RequestId;
+use codex_exec_server_protocol::JSONRPCMessage;
+use codex_exec_server_protocol::JSONRPCNotification;
+use codex_exec_server_protocol::JSONRPCRequest;
+use codex_exec_server_protocol::JSONRPCResponse;
+use codex_exec_server_protocol::RequestId;
 use pretty_assertions::assert_eq;
 use tokio::io::AsyncBufReadExt;
 use tokio::io::AsyncWriteExt;
@@ -74,7 +74,6 @@ async fn stdio_listen_transport_serves_initialize() {
             })
             .expect("initialize params should serialize"),
         ),
-        trace: None,
     });
     write_jsonrpc_line(&mut client_writer, &initialize).await;