Clean up deployment release flow

[eetoc]

Summary

• keep docker-compose.deploy.yml as the release deployment template and add the missing /dev/kvm device mount
• add an explicit installer deployment plan prompt with --yes / AGENT_COMPOSE_YES=1 for automation
• simplify release assets to install.sh, agent-compose-installer.tar.gz, and SHASUMS256.txt
• add a CI coverage gate using the existing scripts/test-coverage.sh thresholds

Checks

• python YAML parse for .github/workflows/ci.yml and .github/workflows/images.yml
• bash -n deploy/install.sh
• docker compose -f docker-compose.deploy.yml config

Note: full coverage execution was not completed locally; only syntax/config checks were run before committing.