Request compression.

Add new model_provider flag for compression to enable request
compression.  We support zstd and gzip, server also supports brotli

You can test this against the sign in with chatgpt flow by adding the
following profile:

```
[profiles.compressed]
name = "compressed"
model_provider = "openai-zstd"

[model_providers.openai-zstd]
name = "OpenAI (ChatGPT, zstd)"
wire_api = "responses"
request_compression = "zstd"
requires_openai_auth = true
```

This will zstd compress your request before sending it to the server.

codex-rs/codex-client/src/default_client.rs

@@ -104,6 +104,13 @@ impl CodexRequestBuilder {
         self.map(|builder| builder.json(value))
     }
 
+    pub fn body<T>(self, body: T) -> Self
+    where
+        T: Into<reqwest::Body>,
+    {
+        self.map(|builder| builder.body(body))
+    }
+
     pub async fn send(self) -> Result<Response, reqwest::Error> {
         let headers = trace_headers();
 

codex-rs/codex-client/src/lib.rs

@@ -10,6 +10,7 @@ pub use crate::default_client::CodexHttpClient;
 pub use crate::default_client::CodexRequestBuilder;
 pub use crate::error::StreamError;
 pub use crate::error::TransportError;
+pub use crate::request::Body;
 pub use crate::request::Request;
 pub use crate::request::Response;
 pub use crate::retry::RetryOn;

codex-rs/codex-client/src/request.rs

@@ -5,12 +5,18 @@ use serde::Serialize;
 use serde_json::Value;
 use std::time::Duration;
 
+#[derive(Debug, Clone)]
+pub enum Body {
+    Json(Value),
+    Bytes(Bytes),
+}
+
 #[derive(Debug, Clone)]
 pub struct Request {
     pub method: Method,
     pub url: String,
     pub headers: HeaderMap,
-    pub body: Option<Value>,
+    pub body: Option<Body>,
     pub timeout: Option<Duration>,
 }
 
@@ -26,7 +32,7 @@ impl Request {
     }
 
     pub fn with_json<T: Serialize>(mut self, body: &T) -> Self {
-        self.body = serde_json::to_value(body).ok();
+        self.body = serde_json::to_value(body).ok().map(Body::Json);
         self
     }
 }

codex-rs/codex-client/src/transport.rs

@@ -1,6 +1,7 @@
 use crate::default_client::CodexHttpClient;
 use crate::default_client::CodexRequestBuilder;
 use crate::error::TransportError;
+use crate::request::Body;
 use crate::request::Request;
 use crate::request::Response;
 use async_trait::async_trait;
@@ -52,7 +53,10 @@ impl ReqwestTransport {
             builder = builder.timeout(timeout);
         }
         if let Some(body) = req.body {
-            builder = builder.json(&body);
+            builder = match body {
+                Body::Json(value) => builder.json(&value),
+                Body::Bytes(bytes) => builder.body(bytes),
+            };
         }
         Ok(builder)
     }
@@ -101,10 +105,10 @@ impl HttpTransport for ReqwestTransport {
     async fn stream(&self, req: Request) -> Result<StreamResponse, TransportError> {
         if enabled!(Level::TRACE) {
             trace!(
-                "{} to {}: {}",
-                req.method,
-                req.url,
-                req.body.as_ref().unwrap_or_default()
+                method = %req.method,
+                url = %req.url,
+                body = ?req.body,
+                "Sending streaming request"
             );
         }