Use supports_color in codex exec (#4633)

It knows how to detect github actions

codex-rs/Cargo.lock

@@ -929,6 +929,7 @@ dependencies = [
  "serde",
  "serde_json",
  "shlex",
+ "supports-color",
  "tempfile",
  "tokio",
  "tracing",

codex-rs/exec/Cargo.toml

@@ -31,6 +31,7 @@ owo-colors = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 shlex = { workspace = true }
+supports-color = { workspace = true }
 tokio = { workspace = true, features = [
     "io-std",
     "macros",

codex-rs/exec/src/lib.rs

@@ -28,6 +28,7 @@ use serde_json::Value;
 use std::io::IsTerminal;
 use std::io::Read;
 use std::path::PathBuf;
+use supports_color::Stream;
 use tracing::debug;
 use tracing::error;
 use tracing::info;
@@ -113,8 +114,8 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
         cli::Color::Always => (true, true),
         cli::Color::Never => (false, false),
         cli::Color::Auto => (
-            std::io::stdout().is_terminal(),
+            supports_color::on_cached(Stream::Stdout).is_some(),
-            std::io::stderr().is_terminal(),
+            supports_color::on_cached(Stream::Stderr).is_some(),
         ),
     };