exec-server: additional context for errors (#7935)

Add a .context() on some exec-server errors for debugging CI flakes.

Also, "login": false in the test to make the test not affected by user
profile.

codex-rs/exec-server/src/posix/escalate_client.rs

@@ -51,7 +51,10 @@ pub(crate) async fn run(file: String, argv: Vec<String>) -> anyhow::Result<i32>
         })
         .await
         .context("failed to send EscalateRequest")?;
-    let message = client.receive::<EscalateResponse>().await?;
+    let message = client
+        .receive::<EscalateResponse>()
+        .await
+        .context("failed to receive EscalateResponse")?;
     match message.action {
         EscalateAction::Escalate => {
             // TODO: maybe we should send ALL open FDs (except the escalate client)?