Add remote env CI matrix and integration test (#14869)

`CODEX_TEST_REMOTE_ENV` will make `test_codex` start the executor
"remotely" (inside a docker container) turning any integration test into
remote test.

scripts/test-remote-env.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+
+# Remote-env setup script for codex-rs integration tests.
+#
+# Usage (source-only):
+#   source scripts/test-remote-env.sh
+#   cd codex-rs
+#   cargo test -p codex-core --test all remote_env_connects_creates_temp_dir_and_runs_sample_script
+#   codex_remote_env_cleanup
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+is_sourced() {
+  [[ "${BASH_SOURCE[0]}" != "$0" ]]
+}
+
+setup_remote_env() {
+  local container_name
+  local codex_exec_server_binary_path
+
+  container_name="${CODEX_TEST_REMOTE_ENV_CONTAINER_NAME:-codex-remote-test-env-local-$(date +%s)-${RANDOM}}"
+  codex_exec_server_binary_path="${REPO_ROOT}/codex-rs/target/debug/codex-exec-server"
+
+  if ! command -v docker >/dev/null 2>&1; then
+    echo "docker is required (Colima or Docker Desktop)" >&2
+    return 1
+  fi
+
+  if ! docker info >/dev/null 2>&1; then
+    echo "docker daemon is not reachable; for Colima run: colima start" >&2
+    return 1
+  fi
+
+  if ! command -v cargo >/dev/null 2>&1; then
+    echo "cargo is required to build codex-exec-server" >&2
+    return 1
+  fi
+
+  (
+    cd "${REPO_ROOT}/codex-rs"
+    cargo build -p codex-exec-server --bin codex-exec-server
+  )
+
+  if [[ ! -f "${codex_exec_server_binary_path}" ]]; then
+    echo "codex-exec-server binary not found at ${codex_exec_server_binary_path}" >&2
+    return 1
+  fi
+
+  docker rm -f "${container_name}" >/dev/null 2>&1 || true
+  docker run -d --name "${container_name}" ubuntu:24.04 sleep infinity >/dev/null
+
+  export CODEX_TEST_REMOTE_ENV="${container_name}"
+}
+
+codex_remote_env_cleanup() {
+  if [[ -n "${CODEX_TEST_REMOTE_ENV:-}" ]]; then
+    docker rm -f "${CODEX_TEST_REMOTE_ENV}" >/dev/null 2>&1 || true
+    unset CODEX_TEST_REMOTE_ENV
+  fi
+}
+
+if ! is_sourced; then
+  echo "source this script instead of executing it: source scripts/test-remote-env.sh" >&2
+  exit 1
+fi
+
+old_shell_options="$(set +o)"
+set -euo pipefail
+if setup_remote_env; then
+  status=0
+  echo "CODEX_TEST_REMOTE_ENV=${CODEX_TEST_REMOTE_ENV}"
+  echo "Remote env ready. Run your command, then call: codex_remote_env_cleanup"
+else
+  status=$?
+fi
+eval "${old_shell_options}"
+return "${status}"