[codex] migrate ExecutorFileSystem paths to PathUri (#27424)

## Why

We're moving exec-server to use PathUri for its internal path
representations.

## What

Move `ExecutorFileSystem` APIs to use `PathUri` instead of
`AbsolutePathBuf`. Future changes will convert higher-level parts of
exec-server.

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

@@ -0,0 +1,225 @@
+#![allow(clippy::expect_used)]
+
+#[cfg(windows)]
+use codex_app_server_protocol::JSONRPCMessage;
+#[cfg(windows)]
+use codex_app_server_protocol::JSONRPCResponse;
+#[cfg(windows)]
+use codex_utils_absolute_path::AbsolutePathBuf;
+use codex_utils_path_uri::PathUri;
+#[cfg(windows)]
+use futures::SinkExt;
+#[cfg(windows)]
+use futures::StreamExt;
+use pretty_assertions::assert_eq;
+use tokio::io;
+#[cfg(windows)]
+use tokio::net::TcpListener;
+#[cfg(windows)]
+use tokio::net::TcpStream;
+#[cfg(windows)]
+use tokio::sync::oneshot;
+#[cfg(windows)]
+use tokio::time::Duration;
+#[cfg(windows)]
+use tokio::time::timeout;
+#[cfg(windows)]
+use tokio_tungstenite::WebSocketStream;
+#[cfg(windows)]
+use tokio_tungstenite::accept_async;
+#[cfg(windows)]
+use tokio_tungstenite::tungstenite::Message;
+
+use super::*;
+use crate::client_api::ExecServerTransportParams;
+#[cfg(windows)]
+use crate::protocol::FS_READ_FILE_METHOD;
+#[cfg(windows)]
+use crate::protocol::FsReadFileParams;
+#[cfg(windows)]
+use crate::protocol::FsReadFileResponse;
+#[cfg(windows)]
+use crate::protocol::INITIALIZE_METHOD;
+#[cfg(windows)]
+use crate::protocol::INITIALIZED_METHOD;
+#[cfg(windows)]
+use crate::protocol::InitializeResponse;
+
+#[tokio::test]
+async fn non_native_uri_is_rejected_before_connecting() {
+    let file_system = RemoteFileSystem::new(LazyRemoteExecServerClient::new(
+        ExecServerTransportParams::websocket_url("not a websocket URL".to_string()),
+    ));
+
+    let error = file_system
+        .read_file(&non_native_uri(), /*sandbox*/ None)
+        .await
+        .expect_err("non-native URI should be rejected");
+
+    assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
+}
+
+#[cfg(windows)]
+#[tokio::test]
+async fn remote_file_system_sends_explicit_windows_native_paths() {
+    let (websocket_url, captured_paths, server) = record_read_file_paths(2).await;
+    let file_system = RemoteFileSystem::new(LazyRemoteExecServerClient::new(
+        ExecServerTransportParams::websocket_url(websocket_url),
+    ));
+    let paths = vec![
+        (
+            PathUri::parse("file:///C:/Users/Alice/src/main.rs").expect("valid drive URI"),
+            absolute_windows_path(r"C:\Users\Alice\src\main.rs"),
+        ),
+        (
+            PathUri::parse("file://server/share/src/main.rs").expect("valid UNC URI"),
+            absolute_windows_path(r"\\server\share\src\main.rs"),
+        ),
+    ];
+    let expected_paths = paths
+        .iter()
+        .map(|(_, expected_path)| expected_path.clone())
+        .collect::<Vec<_>>();
+
+    for (path, _) in paths {
+        assert_eq!(
+            file_system
+                .read_file(&path, /*sandbox*/ None)
+                .await
+                .expect("remote read should succeed"),
+            Vec::<u8>::new()
+        );
+    }
+
+    assert_eq!(
+        captured_paths.await.expect("captured paths"),
+        expected_paths
+    );
+    server.await.expect("recording server should succeed");
+}
+
+fn non_native_uri() -> PathUri {
+    #[cfg(unix)]
+    let uri = "file://server/share/file.txt";
+    #[cfg(windows)]
+    let uri = "file:///usr/local/file.txt";
+
+    PathUri::parse(uri).expect("valid non-native URI")
+}
+
+#[cfg(windows)]
+fn absolute_windows_path(path: &str) -> AbsolutePathBuf {
+    AbsolutePathBuf::from_absolute_path_checked(path).expect("absolute Windows path")
+}
+
+#[cfg(windows)]
+async fn record_read_file_paths(
+    expected_requests: usize,
+) -> (
+    String,
+    oneshot::Receiver<Vec<AbsolutePathBuf>>,
+    tokio::task::JoinHandle<()>,
+) {
+    let listener = TcpListener::bind("127.0.0.1:0")
+        .await
+        .expect("listener should bind");
+    let websocket_url = format!("ws://{}", listener.local_addr().expect("listener address"));
+    let (captured_paths_tx, captured_paths_rx) = oneshot::channel();
+    let server = tokio::spawn(async move {
+        let (stream, _) = listener.accept().await.expect("listener should accept");
+        let mut websocket = accept_async(stream)
+            .await
+            .expect("websocket handshake should succeed");
+        complete_websocket_initialize(&mut websocket).await;
+
+        let mut captured_paths = Vec::with_capacity(expected_requests);
+        for _ in 0..expected_requests {
+            let request = match read_jsonrpc_websocket(&mut websocket).await {
+                JSONRPCMessage::Request(request) if request.method == FS_READ_FILE_METHOD => {
+                    request
+                }
+                other => panic!("expected fs/readFile request, got {other:?}"),
+            };
+            let params: FsReadFileParams =
+                serde_json::from_value(request.params.expect("fs/readFile params should exist"))
+                    .expect("fs/readFile params should deserialize");
+            captured_paths.push(params.path);
+            write_jsonrpc_websocket(
+                &mut websocket,
+                JSONRPCMessage::Response(JSONRPCResponse {
+                    id: request.id,
+                    result: serde_json::to_value(FsReadFileResponse {
+                        data_base64: String::new(),
+                    })
+                    .expect("fs/readFile response should serialize"),
+                }),
+            )
+            .await;
+        }
+        captured_paths_tx
+            .send(captured_paths)
+            .expect("captured paths receiver should stay open");
+    });
+
+    (websocket_url, captured_paths_rx, server)
+}
+
+#[cfg(windows)]
+async fn complete_websocket_initialize(websocket: &mut WebSocketStream<TcpStream>) {
+    let request = match read_jsonrpc_websocket(websocket).await {
+        JSONRPCMessage::Request(request) if request.method == INITIALIZE_METHOD => request,
+        other => panic!("expected initialize request, got {other:?}"),
+    };
+    write_jsonrpc_websocket(
+        websocket,
+        JSONRPCMessage::Response(JSONRPCResponse {
+            id: request.id,
+            result: serde_json::to_value(InitializeResponse {
+                session_id: "session-1".to_string(),
+            })
+            .expect("initialize response should serialize"),
+        }),
+    )
+    .await;
+
+    match read_jsonrpc_websocket(websocket).await {
+        JSONRPCMessage::Notification(notification) if notification.method == INITIALIZED_METHOD => {
+        }
+        other => panic!("expected initialized notification, got {other:?}"),
+    }
+}
+
+#[cfg(windows)]
+async fn read_jsonrpc_websocket(websocket: &mut WebSocketStream<TcpStream>) -> JSONRPCMessage {
+    loop {
+        match timeout(Duration::from_secs(1), websocket.next())
+            .await
+            .expect("json-rpc websocket read should not time out")
+            .expect("websocket should stay open")
+            .expect("websocket frame should read")
+        {
+            Message::Text(text) => {
+                return serde_json::from_str(text.as_ref())
+                    .expect("json-rpc text frame should parse");
+            }
+            Message::Binary(bytes) => {
+                return serde_json::from_slice(bytes.as_ref())
+                    .expect("json-rpc binary frame should parse");
+            }
+            Message::Ping(_) | Message::Pong(_) => {}
+            other => panic!("expected json-rpc websocket frame, got {other:?}"),
+        }
+    }
+}
+
+#[cfg(windows)]
+async fn write_jsonrpc_websocket(
+    websocket: &mut WebSocketStream<TcpStream>,
+    message: JSONRPCMessage,
+) {
+    let encoded = serde_json::to_string(&message).expect("json-rpc should serialize");
+    websocket
+        .send(Message::Text(encoded.into()))
+        .await
+        .expect("json-rpc websocket frame should write");
+}