## Why
The Desktop app can use Codex or ChatGPT branding while retaining stable platform identities. CLI discovery and TUI handoff should not depend on a single display name or hardcoded executable path.
## What changed
- On macOS, search for both `ChatGPT.app` and `Codex.app`, and accept only bundles with the `com.openai.codex` identifier.
- On Windows, detect installs by their package app ID and resolve the `codex` protocol executable from the AppX manifest before handing off a TUI session.
- Use “Desktop app” consistently in CLI and TUI user-facing text.
## Testing
Add coverage for selecting a ChatGPT-named Codex bundle and rejecting the classic ChatGPT bundle.
GitOrigin-RevId: b84a56eb6e960712152e1a9b023ab530ec9a354a