docs: add Next Steps After Setup section to clarify onboarding (#2047)

[vinodkadli7022]

Description

This PR improves onboarding clarity by documenting what users should do after running quickstart.sh, especially for those who choose not to use Claude Code.

It adds a clear, minimal manual workflow for creating, validating, and running agents, reducing confusion for first-time contributors.

Type of Change

• Documentation update

Related Issues

Fixes #2047

Changes Made

• Added a Next Steps After Setup section to the environment setup docs
• Clarified that Claude Code is recommended but optional
• Documented a minimal manual path for building and validating agents
• Improved structure and readability for new users

Testing

• Manual testing performed
  • Verified documentation flow
  • Confirmed commands and paths are accurate

Checklist

• My changes follow the project's documentation style
• I have performed a self-review of my changes
• I have made corresponding documentation updates
• My changes introduce no new warnings

Screenshots (if applicable)

N/A – documentation-only changes