docs: update deployment guide with optimized setup script

Updated CLOUD-AGENTS-READY.md to include both setup scripts:
- Full installation for fresh Ubuntu 24.04
- Optimized installation for pre-configured base images (RECOMMENDED)

Highlights:
- Optimized script detects existing tools
- Much faster execution (1-2 min vs 5-10 min)
- Recommended for the provided Dockerfile base image
- Clear usage examples for both scripts

Users with the provided Dockerfile should use setup-cloud-agent-env-optimized.sh