Fix Windows Codex preflight for v1.0.9

[squarepots]

Summary

Public v1.0.8 still blocks a saved-account switch before credential replacement with a Codex configuration-check error. The installed official Windows npm CLI ships a native codex.exe, but GSwitch launched its Node wrapper from the desktop process. That adds a Node PATH dependency and an extra child process during isolated-profile cleanup.

• Start the native executable shipped by the installed Codex npm package, retaining the existing fallback when it is absent.
• Distinguish App Server startup, configuration read, and temporary-profile cleanup failures with safe English and Chinese messages.
• Synchronize the patch version to 1.0.9.

Refs #119. The Issue stays open for maintainer validation with real saved accounts in the public Windows build.

Focused proof

• Native launcher regression test passed.
• Installed Codex 0.144.5 App Server read and wrote an isolated configuration, then removed the profile, with Node absent from PATH.
• Account UI tests: 61 passed; frontend production build and version synchronization passed.
• No real account switch, Wake, or credential write was performed.