Fix Linux workspace visibility and desktop status

[ccofallen]

Summary

• keep the Linux pet visible across workspaces with Electron's non-focusable window policy
• preserve drag and right-click IPC paths and keep Windows/macOS policies unchanged
• replace browser-only lifecycle warnings in packaged settings with accurate desktop background guidance
• bump the desktop release to 0.2.2

Verification

• full desktop release gate passed locally
• 700 unit tests, 6 Electron tests, and 40 Playwright E2E tests passed
• final whole-branch review passed after all findings were addressed

Platform scope

• Linux all-workspace behavior follows Electron's documented contract; native dragging remains compositor-dependent on Wayland
• Windows remains always on top in the current virtual desktop
• macOS all-spaces/fullscreen behavior is unchanged