Updates now detect a missing native binary instead of reporting success

What

When Claude Code updates itself through npm or bun, the download includes a separate package with the program built for your platform, called the native binary. If that package is missing, what gets installed is only a placeholder. The updater now catches this.

• After npm or bun reports success, the updater runs the installed claude with --version. If it is still the placeholder stub, the update fails with the hint native_binary_missing. If npm's ignore-scripts is set, or the test cannot tell either way, the success exit code is trusted as before.
• Install output saying a native package was not found is now classed as native_package_missing. The updater then reports install_failed and notes that npm should have restored the previous version.
• claude update prints an error that the native binary for this platform was not downloaded and tells you to run claude update again or reinstall with npm.
• The auto-update status now shows a specific hint: native binary for this platform was not downloaded (will retry), or claude.exe in use (close other Claude Code sessions, including VS Code) when Windows has the program file locked.
• The Update installed · message now ends with either a component or Restart to update.

Why

Before, an update could look successful while leaving behind a stub that does not run. You now get a failure that says what went wrong and what to do, and Windows users see why an update was blocked.