create codex configuration

codex/lib.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+log() {
+  printf '[codex] %s\n' "$*"
+}
+
+warn() {
+  printf '[codex][warn] %s\n' "$*" >&2
+}
+
+die() {
+  printf '[codex][error] %s\n' "$*" >&2
+  exit 1
+}
+
+have() {
+  command -v "$1" >/dev/null 2>&1
+}
+
+repo_root() {
+  git rev-parse --show-toplevel 2>/dev/null || pwd
+}
+
+cd_repo_root() {
+  cd "$(repo_root)"
+}
+
+ensure_file() {
+  local path="$1"
+  [[ -f "$path" ]] || die "Required file not found: $path"
+}
+
+ensure_dir() {
+  local path="$1"
+  mkdir -p "$path"
+}
+
+append_if_missing() {
+  local line="$1"
+  local file="$2"
+  touch "$file"
+  grep -Fqx "$line" "$file" || printf '%s\n' "$line" >> "$file"
+}