Removes the standalone `DesktopShellBootstrap` component from the desktop package, routing desktop remote mode into the shell onboarding flow instead. Updates the corresponding test file to reflect the component removal and adjusts the README.
Fusion-Task-Id: FN-3399
The merge lands Step 7 of FN-3398, adding documentation and delivery artifacts across the mobile and desktop packages with updated READMEs, mobile-specific docs, and architecture references.
Fusion-Task-Id: FN-3398