Support packaged managed Codex binary paths (#42318)

## What changed

- Prefer the managed executable under `packages/standalone/current/bin` when it exists.
- Fall back to the legacy `packages/standalone/current` executable layout.
- Preserve platform-specific missing-install paths so launch validation and lifecycle commands continue to behave as expected.

## Testing

- Add a path-selection test covering missing, legacy, and packaged installs.

GitOrigin-RevId: 4c0d066257e9984a35e3b95dd83c768d9ce69431

codex-rs/app-server-daemon/src/managed_install.rs

@@ -1,3 +1,5 @@
+//! Resolves packaged and legacy standalone install layouts.
+
 use std::path::Path;
 use std::path::PathBuf;
 
@@ -16,12 +18,23 @@ use tokio::fs;
 #[cfg(unix)]
 use tokio::process::Command;
 
+/// Returns the packaged executable when present, otherwise an existing legacy executable.
+/// If neither exists, returns the expected packaged path on Windows and preserves the
+/// historical legacy fallback on Unix. This is path selection, not existence validation:
+/// launch operations reject a missing executable separately, while commands such as
+/// stop can still run after the managed install has been removed.
 pub(crate) fn managed_codex_bin(codex_home: &Path) -> PathBuf {
-    codex_home
+    let current = codex_home
         .join("packages")
         .join("standalone")
-        .join("current")
-        .join(managed_codex_file_name())
+        .join("current");
+    let packaged = current.join("bin").join(managed_codex_file_name());
+    let legacy = current.join(managed_codex_file_name());
+    if packaged.is_file() || (cfg!(windows) && !legacy.is_file()) {
+        packaged
+    } else {
+        legacy
+    }
 }
 
 #[cfg(unix)]
@@ -101,3 +114,7 @@ fn parse_codex_version(output: &str) -> Result<String> {
 #[cfg(all(test, unix))]
 #[path = "managed_install_tests.rs"]
 mod tests;
+
+#[cfg(test)]
+#[path = "managed_install_path_tests.rs"]
+mod path_tests;

codex-rs/app-server-daemon/src/managed_install_path_tests.rs

@@ -0,0 +1,21 @@
+use pretty_assertions::assert_eq;
+
+#[test]
+fn discovers_package_and_legacy_installs() {
+    let home = tempfile::TempDir::new().expect("home");
+    let current = home.path().join("packages/standalone/current");
+    let legacy = current.join(super::managed_codex_file_name());
+    let expected = if cfg!(windows) {
+        current.join("bin").join("codex.exe")
+    } else {
+        legacy.clone()
+    };
+    assert_eq!(super::managed_codex_bin(home.path()), expected);
+    std::fs::create_dir_all(&current).expect("current directory");
+    std::fs::write(&legacy, b"legacy").expect("legacy executable");
+    assert_eq!(super::managed_codex_bin(home.path()), legacy);
+    let packaged = current.join("bin").join(super::managed_codex_file_name());
+    std::fs::create_dir(current.join("bin")).expect("bin directory");
+    std::fs::write(&packaged, b"packaged").expect("packaged executable");
+    assert_eq!(super::managed_codex_bin(home.path()), packaged);
+}