Add in-process app server and wire up exec to use it (#14005)

This is a subset of PR #13636. See that PR for a full overview of the
architectural change.

This PR implements the in-process app server and modifies the
non-interactive "exec" entry point to use the app server.

---------

Co-authored-by: Felipe Coury <felipe.coury@gmail.com>

codex-rs/app-server/src/app_server_tracing.rs

@@ -1,6 +1,16 @@
+//! Tracing helpers shared by socket and in-process app-server entry points.
+//!
+//! The in-process path intentionally reuses the same span shape as JSON-RPC
+//! transports so request telemetry stays comparable across stdio, websocket,
+//! and embedded callers. [`typed_request_span`] is the in-process counterpart
+//! of [`request_span`] and stamps `rpc.transport` as `"in-process"` while
+//! deriving client identity from the typed [`ClientRequest`] rather than
+//! from a parsed JSON envelope.
+
 use crate::message_processor::ConnectionSessionState;
 use crate::outgoing_message::ConnectionId;
 use crate::transport::AppServerTransport;
+use codex_app_server_protocol::ClientRequest;
 use codex_app_server_protocol::InitializeParams;
 use codex_app_server_protocol::JSONRPCRequest;
 use codex_otel::set_parent_from_context;
@@ -65,6 +75,51 @@ pub(crate) fn request_span(
     span
 }
 
+/// Builds tracing span metadata for typed in-process requests.
+///
+/// This mirrors `request_span` semantics while stamping transport as
+/// `in-process` and deriving client info either from initialize params or
+/// from existing connection session state.
+pub(crate) fn typed_request_span(
+    request: &ClientRequest,
+    connection_id: ConnectionId,
+    session: &ConnectionSessionState,
+) -> Span {
+    let method = request.method();
+    let span = info_span!(
+        "app_server.request",
+        otel.kind = "server",
+        otel.name = method,
+        rpc.system = "jsonrpc",
+        rpc.method = method,
+        rpc.transport = "in-process",
+        rpc.request_id = ?request.id(),
+        app_server.connection_id = ?connection_id,
+        app_server.api_version = "v2",
+        app_server.client_name = field::Empty,
+        app_server.client_version = field::Empty,
+    );
+
+    if let Some((client_name, client_version)) = initialize_client_info_from_typed_request(request)
+    {
+        span.record("app_server.client_name", client_name);
+        span.record("app_server.client_version", client_version);
+    } else {
+        if let Some(client_name) = session.app_server_client_name.as_deref() {
+            span.record("app_server.client_name", client_name);
+        }
+        if let Some(client_version) = session.client_version.as_deref() {
+            span.record("app_server.client_version", client_version);
+        }
+    }
+
+    if let Some(context) = traceparent_context_from_env() {
+        set_parent_from_context(&span, context);
+    }
+
+    span
+}
+
 fn transport_name(transport: AppServerTransport) -> &'static str {
     match transport {
         AppServerTransport::Stdio => "stdio",
@@ -99,3 +154,13 @@ fn initialize_client_info(request: &JSONRPCRequest) -> Option<InitializeParams>
     let params = request.params.clone()?;
     serde_json::from_value(params).ok()
 }
+
+fn initialize_client_info_from_typed_request(request: &ClientRequest) -> Option<(&str, &str)> {
+    match request {
+        ClientRequest::Initialize { params, .. } => Some((
+            params.client_info.name.as_str(),
+            params.client_info.version.as_str(),
+        )),
+        _ => None,
+    }
+}