feat(tunnel): 请求体流式传输 & OpenAI CLI 请求 key 排序优化

Hub 端:
- open_local_stream 不再接收 body 参数，改为通过 push_local_request_body 分块推送
- 请求体按 32KB 分帧发送，避免大请求一次性压缩和传输
- local_relay 改为流式解析 envelope 和转发请求体

Proxy 端:
- stream_handler 改为流式传输请求体到上游，不再预先收集完整 body
- upstream_client 请求体类型从 Full<Bytes> 改为 UnsyncBoxBody 以支持流式传输
- dispatcher 将 StreamEnd/StreamError 事件转发给 stream handler

Python 端:
- hub_transport relay envelope 改为异步生成器流式发送
- 提取 reorder_openai_cli_request_prefix_keys 为公共函数
- Codex passthrough 路径也应用稳定的前缀 key 排序

aether-hub/Cargo.toml

@@ -18,6 +18,7 @@ flate2 = "1"
 futures-util = "0.3"
 bytes = "1"
 async-stream = "0.3"
+http-body-util = "0.1"
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
 
 [profile.release]