Adding an AGENTS.md file for Codex use

Added the `instructions` attribute to the MCP servers to solve openai#704 .

Let me know if you want to add an example to the documentation.

PR to enhance the `Usage` object and related logic, to support more
granular token accounting, matching the details available in the [OpenAI
Responses API](https://platform.openai.com/docs/api-reference/responses)
. Specifically, it:

- Adds `input_tokens_details` and `output_tokens_details` fields to the
`Usage` dataclass, storing detailed token breakdowns (e.g.,
`cached_tokens`, `reasoning_tokens`).
- Flows this change through
- Updates and extends tests to match
- Adds a test for the Usage.add method

### Motivation
- Aligns the SDK’s usage with the latest OpenAI responses API Usage
object
- Supports downstream use cases that require fine-grained token usage
data (e.g., billing, analytics, optimization) requested by startups

---------

Co-authored-by: Wulfie Bain <[email protected]>

---
[//]: # (BEGIN SAPLING FOOTER)
* openai#732
* openai#731
* __->__ openai#730

---
[//]: # (BEGIN SAPLING FOOTER)
* openai#732
* __->__ openai#731

…penai#732)

Fix for openai#734

## Summary
- avoid infinite recursion in visualization by tracking visited agents
- test cycle detection in graph utility

## Testing
- `make mypy`
- `make tests` 

Resolves openai#668

## Summary
- mention MCPServerStreamableHttp in MCP server docs
- document CodeInterpreterTool, HostedMCPTool, ImageGenerationTool and
LocalShellTool
- update Japanese translations

## Summary
- avoid AttributeError when Gemini API returns `None` for chat message
- return empty output if message is filtered
- add regression test

## Testing
- `make format`
- `make lint`
- `make mypy`
- `make tests`

Towards openai#744