Propagate installer download failures in standalone Unix updates (#57208)

## Why

The standalone Unix update pipeline could return success when `curl` failed because the shell consuming its output exited successfully.

## What changed

Download the installer into a shell variable and evaluate it only after a successful download, preserving `CODEX_NON_INTERACTIVE=1`. Update the displayed update command to match.

## Testing

Add a Unix regression test that forces an installer download failure and asserts a nonzero exit status. Update the update-available snapshot for the new command.

GitOrigin-RevId: cf6ce0dae483203e3609bb35f35eb04bb3096c28

codex-rs/tui/src/history_cell/snapshots/codex_tui__history_cell__tests__standalone_unix_update_available_history_cell_snapshot.snap

@@ -2,10 +2,11 @@
 source: tui/src/history_cell/tests.rs
 expression: rendered
 ---
-╭─────────────────────────────────────────────────────────────────────────────────────────────────────╮
-│ ✨ Update available! 0.0.0 -> 9.9.9                                                                 │
-│ Run sh -c 'curl -fsSL https://chatgpt.com/codex/install.sh | CODEX_NON_INTERACTIVE=1 sh' to update. │
-│                                                                                                     │
-│ See full release notes:                                                                             │
-│ https://github.com/openai/codex/releases/latest                                                     │
-╰─────────────────────────────────────────────────────────────────────────────────────────────────────╯
+╭────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
+│ ✨ Update available! 0.0.0 -> 9.9.9                                                                        │
+│ Run sh -c 's=$(curl -fsSL https://chatgpt.com/codex/install.sh) && CODEX_NON_INTERACTIVE=1 eval "$s"' to   │
+│ update.                                                                                                    │
+│                                                                                                            │
+│ See full release notes:                                                                                    │
+│ https://github.com/openai/codex/releases/latest                                                            │
+╰────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

codex-rs/tui/src/update_action.rs

@@ -20,7 +20,7 @@ pub enum UpdateAction {
     PnpmGlobalLatest,
     /// Update via `brew upgrade codex`.
     BrewUpgrade,
-    /// Update via `curl -fsSL https://chatgpt.com/codex/install.sh | CODEX_NON_INTERACTIVE=1 sh`.
+    /// Update via the standalone Unix installer.
     StandaloneUnix,
     /// Update via `$env:CODEX_NON_INTERACTIVE=1; irm https://chatgpt.com/codex/install.ps1 | iex`.
     StandaloneWindows,
@@ -56,7 +56,7 @@ impl UpdateAction {
                 "sh",
                 &[
                     "-c",
-                    "curl -fsSL https://chatgpt.com/codex/install.sh | CODEX_NON_INTERACTIVE=1 sh",
+                    r#"s=$(curl -fsSL https://chatgpt.com/codex/install.sh) && CODEX_NON_INTERACTIVE=1 eval "$s""#,
                 ],
             ),
             UpdateAction::StandaloneWindows => (
@@ -156,17 +156,7 @@ mod tests {
     }
 
     #[test]
-    fn standalone_update_commands_rerun_latest_installer() {
-        assert_eq!(
-            UpdateAction::StandaloneUnix.command_args(),
-            (
-                "sh",
-                &[
-                    "-c",
-                    "curl -fsSL https://chatgpt.com/codex/install.sh | CODEX_NON_INTERACTIVE=1 sh"
-                ][..],
-            )
-        );
+    fn standalone_windows_update_command_reruns_latest_installer() {
         assert_eq!(
             UpdateAction::StandaloneWindows.command_args(),
             (
@@ -180,6 +170,23 @@ mod tests {
             )
         );
     }
+
+    #[cfg(unix)]
+    #[test]
+    fn standalone_unix_update_fails_when_installer_download_fails() {
+        let (command, args) = UpdateAction::StandaloneUnix.command_args();
+        let offline_command = args[1].replace("https://chatgpt.com", "file:///dev/null");
+        assert_ne!(offline_command, args[1], "installer URL must be replaced");
+        let output = std::process::Command::new(command)
+            .args([args[0], &offline_command])
+            .env_clear()
+            .env("HOME", "/dev/null")
+            .env("PATH", "/usr/bin:/bin")
+            .output()
+            .expect("run standalone Unix update command");
+
+        assert!(!output.status.success(), "{output:?}");
+    }
 }
 
 /// Package source explicitly selected by the user in the daemon menu.