Detect standalone installs from the macOS CLI bundle (#42068)

## What changed

- Recognize executables under `CodexCLI.app/Contents/MacOS` and resolve the
  surrounding standalone package layout from its sibling `bin` directory.
- Preserve standalone install detection and access to bundled resources and
  path entries when Codex is launched through the app bundle.

## Testing

- Add a regression test for package layout and install method discovery from a
  bundled executable.

GitOrigin-RevId: 02b41a978b256da43df95a922bc5ee99a78b8168

codex-rs/install-context/src/bundle_tests.rs

@@ -0,0 +1,48 @@
+//! Ensure a provisioned CLI still discovers its outer package and install method.
+
+use super::*;
+use pretty_assertions::assert_eq;
+use std::fs;
+
+#[test]
+fn bundle_executable_preserves_package_layout_and_install_method() -> std::io::Result<()> {
+    let home = tempfile::tempdir()?;
+    let package = home.path().join("packages/standalone/releases/test");
+    let executable = package.join("CodexCLI.app/Contents/MacOS/codex");
+    fs::create_dir_all(executable.parent().unwrap())?;
+    fs::write(&executable, "")?;
+    for directory in [BIN_DIRNAME, RESOURCES_DIRNAME, PATH_DIRNAME] {
+        fs::create_dir_all(package.join(directory))?;
+    }
+    fs::write(
+        package.join(PACKAGE_METADATA_FILENAME),
+        r#"{"version":"1.2.3"}"#,
+    )?;
+    let package = canonical_absolute_path(&package).unwrap();
+    let bin_dir = package.join(BIN_DIRNAME);
+    let resources_dir = package.join(RESOURCES_DIRNAME);
+    let path_dir = package.join(PATH_DIRNAME);
+    let context = InstallContext::from_exe_with_codex_home(
+        /*is_macos*/ true,
+        /*current_exe*/ Some(&executable),
+        /*method_override*/ None,
+        /*codex_home*/ Some(home.path()),
+    );
+    assert_eq!(
+        context,
+        InstallContext {
+            method: InstallMethod::Standalone {
+                release_dir: package.clone(),
+                resources_dir: Some(resources_dir.clone()),
+                platform: standalone_platform(),
+            },
+            package_layout: Some(CodexPackageLayout {
+                package_dir: package,
+                bin_dir,
+                resources_dir: Some(resources_dir),
+                path_dir: Some(path_dir),
+            }),
+        }
+    );
+    Ok(())
+}

codex-rs/install-context/src/lib.rs

@@ -248,6 +248,18 @@ impl CodexPackageLayout {
                 let package_dir = exe_dir.parent()?;
                 Self::from_package_bin_dir(package_dir.join(BIN_DIRNAME))
             }
+            Some(name) if name == OsStr::new("MacOS") => {
+                // A provisioned CLI keeps helpers and metadata in the outer
+                // package. current_exe points inside the bundle, not at bin/codex.
+                let contents = exe_dir.parent()?;
+                let bundle = contents.parent()?;
+                if contents.file_name()? != OsStr::new("Contents")
+                    || bundle.file_name()? != OsStr::new("CodexCLI.app")
+                {
+                    return None;
+                }
+                Self::from_package_bin_dir(bundle.parent()?.join(BIN_DIRNAME))
+            }
             Some(_) | None => None,
         }
     }
@@ -344,6 +356,10 @@ fn zsh_resource_path() -> PathBuf {
     PathBuf::from(ZSH_DIRNAME).join(BIN_DIRNAME).join("zsh")
 }
 
+#[cfg(test)]
+#[path = "bundle_tests.rs"]
+mod bundle_tests;
+
 #[cfg(test)]
 mod tests {
     use super::*;