What

Recreate the desktop main window when a second app launch arrives after the original window has already been destroyed.

Why

Packaged Nexu can keep running as a background UIElement app with no remaining windows. In that state, clicking the app again triggers second-instance, but the existing handler only tried to focus an in-memory window reference and could not recover the UI.

How

• add a second-instance fallback that calls createMainWindow() when mainWindow is missing or destroyed
• keep the existing focus path for the normal already-open case
• add a regression invariant test covering the no-window relaunch path

Affected areas

• Desktop app (Electron shell)
• Controller (backend / API)
• Web dashboard (React UI)
• OpenClaw runtime
• Skills
• Shared schemas / packages
• Build / CI / Tooling

Checklist

• pnpm typecheck passes
• pnpm lint passes
• pnpm test passes
• pnpm generate-types run (if API routes/schemas changed)
• No credentials or tokens in code or logs
• No any types introduced (use unknown with narrowing)

Notes for reviewers

This only changes the second-instance recovery path. It does not change the packaged LSUIElement behavior.