fix: sort codex features list alphabetically (#12944)

## Why

`codex features list` currently prints features in declaration order
from `codex_core::features::FEATURES`. That makes the output harder to
scan when looking for a specific flag, and the order can change for
reasons unrelated to the CLI.

## What changed

- Sort the `codex features list` rows by feature key before printing
them in `codex-rs/cli/src/main.rs`.
- Add an integration test in `codex-rs/cli/tests/features.rs` that runs
`codex features list` and asserts the feature-name column is
alphabetized.

## Verification

- Added `features_list_is_sorted_alphabetically_by_feature_name`.
- Ran `cargo test -p codex-cli`.

codex-rs/cli/src/main.rs

@@ -808,6 +808,7 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
                     stage_width = stage_width.max(stage.len());
                     rows.push((name, stage, enabled));
                 }
+                rows.sort_unstable_by_key(|(name, _, _)| *name);
 
                 for (name, stage, enabled) in rows {
                     println!("{name:<name_width$}  {stage:<stage_width$}  {enabled}");

codex-rs/cli/tests/features.rs

@@ -2,6 +2,7 @@ use std::path::Path;
 
 use anyhow::Result;
 use predicates::str::contains;
+use pretty_assertions::assert_eq;
 use tempfile::TempDir;
 
 fn codex_command(codex_home: &Path) -> Result<assert_cmd::Command> {
@@ -58,3 +59,33 @@ async fn features_enable_under_development_feature_prints_warning() -> Result<()
 
     Ok(())
 }
+
+#[tokio::test]
+async fn features_list_is_sorted_alphabetically_by_feature_name() -> Result<()> {
+    let codex_home = TempDir::new()?;
+
+    let mut cmd = codex_command(codex_home.path())?;
+    let output = cmd
+        .args(["features", "list"])
+        .assert()
+        .success()
+        .get_output()
+        .stdout
+        .clone();
+    let stdout = String::from_utf8(output)?;
+
+    let actual_names = stdout
+        .lines()
+        .map(|line| {
+            line.split_once("  ")
+                .map(|(name, _)| name.trim_end().to_string())
+                .expect("feature list output should contain aligned columns")
+        })
+        .collect::<Vec<_>>();
+    let mut expected_names = actual_names.clone();
+    expected_names.sort();
+
+    assert_eq!(actual_names, expected_names);
+
+    Ok(())
+}