Fix Windows auth URL opener

[ishaanxgupta]

What changed

• Replaced the Codex login flow's Windows explorer.exe URL launch path with a guarded shared openUrl helper.
• The Windows path now uses rundll32.exe url.dll,FileProtocolHandler first, with a cmd /c start fallback.
• Added a regression test that verifies the bundled login script contains the safe opener and does not include explorer.exe.
• Fixed Windows test isolation by using fileURLToPath for spawned bundle paths and setting USERPROFILE alongside HOME.
• add /status and /logout

Why

On Windows, launching the long OAuth URL through explorer.exe can be interpreted as a filesystem target instead of a browser URL, causing /supermemory-login to redirect into an internal/local directory rather than the Supermemory authentication flow. This mirrors the issue previously fixed in the Amp plugin.