関連ワード:  what is openai gpt-5-codex    openai gpt 5 codex code refactoring    openai gpt 5 codex release    openai gpt 5 codex agentic coding    openai gpt 5 codex release details    openai codex gpt 5    openai gpt 5 codex in copilot    openai gpt 5 codex model    openai gpt 5 codex api    openai gpt 5 codex preview