Improve error decoding response body error (#5263)

Split Reqwest error into separate error:
1. One for streaming response
2. One for initial connection failing

Include request_id where possible.

<img width="1791" height="116" alt="image"
src="https://github.com/user-attachments/assets/549aa330-acfa-496a-9898-77fa58436316"
/>

codex-rs/core/src/error.rs

@@ -91,6 +91,12 @@ pub enum CodexErr {
     #[error("{0}")]
     UsageLimitReached(UsageLimitReachedError),
 
+    #[error("{0}")]
+    ResponseStreamFailed(ResponseStreamFailed),
+
+    #[error("{0}")]
+    ConnectionFailed(ConnectionFailedError),
+
     #[error(
         "To use Codex with your ChatGPT plan, upgrade to Plus: https://openai.com/chatgpt/pricing."
     )]
@@ -126,9 +132,6 @@ pub enum CodexErr {
     #[error(transparent)]
     Io(#[from] io::Error),
 
-    #[error(transparent)]
-    Reqwest(#[from] reqwest::Error),
-
     #[error(transparent)]
     Json(#[from] serde_json::Error),
 
@@ -147,6 +150,37 @@ pub enum CodexErr {
     EnvVar(EnvVarError),
 }
 
+#[derive(Debug)]
+pub struct ConnectionFailedError {
+    pub source: reqwest::Error,
+}
+
+impl std::fmt::Display for ConnectionFailedError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Connection failed: {}", self.source)
+    }
+}
+
+#[derive(Debug)]
+pub struct ResponseStreamFailed {
+    pub source: reqwest::Error,
+    pub request_id: Option<String>,
+}
+
+impl std::fmt::Display for ResponseStreamFailed {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Error while reading the server response: {}{}",
+            self.source,
+            self.request_id
+                .as_ref()
+                .map(|id| format!(", request id: {id}"))
+                .unwrap_or_default()
+        )
+    }
+}
+
 #[derive(Debug)]
 pub struct UnexpectedResponseError {
     pub status: StatusCode,