Fix: Resolve Missing Agent Initialization in Onboarding Flow

[rogefm]

This fix addresses a critical issue in the onboarding flow where agents were not being properly initialized before proceeding with the setup flow.

Changes made:

• Implemented polling for regular agents in the onboarding/main.cljs module, ensuring agents are loaded before proceeding
• Added agent availability verification before performing actions in onboarding/setup.cljs
• Refactored the verification flow to first check regular agents and then embedded agents
• Enhanced transition state handling with timeouts to improve user experience
• Added loading screens with visual feedback during environment preparation

Benefits:

• Eliminates errors during the onboarding process when users attempt to create connections without agents
• Improved user experience by providing clear feedback during loading
• Ensures all necessary resources are available before allowing user actions