Add codex apply to apply a patch created from the Codex remote agent (#1528)

In order to to this, I created a new `chatgpt` crate where we can put
any code that interacts directly with ChatGPT as opposed to the OpenAI
API. I added a disclaimer to the README for it that it should primarily
be modified by OpenAI employees.


https://github.com/user-attachments/assets/bb978e33-d2c9-4d8e-af28-c8c25b1988e8

codex-rs/chatgpt/src/get_task.rs

@@ -0,0 +1,40 @@
+use codex_core::config::Config;
+use serde::Deserialize;
+
+use crate::chatgpt_client::chatgpt_get_request;
+
+#[derive(Debug, Deserialize)]
+pub struct GetTaskResponse {
+    pub current_diff_task_turn: Option<AssistantTurn>,
+}
+
+// Only relevant fields for our extraction
+#[derive(Debug, Deserialize)]
+pub struct AssistantTurn {
+    pub output_items: Vec<OutputItem>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(tag = "type")]
+pub enum OutputItem {
+    #[serde(rename = "pr")]
+    Pr(PrOutputItem),
+
+    #[serde(other)]
+    Other,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct PrOutputItem {
+    pub output_diff: OutputDiff,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct OutputDiff {
+    pub diff: String,
+}
+
+pub(crate) async fn get_task(config: &Config, task_id: String) -> anyhow::Result<GetTaskResponse> {
+    let path = format!("/wham/tasks/{task_id}");
+    chatgpt_get_request(config, path).await
+}