Rename env vars CAGENT_ to DOCKER_AGENT_ (keep support for old env vars)

[gtardif]

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[docker-agent]

Review Summary

Assessment: 🟢 APPROVE

This PR successfully renames environment variables from CAGENT_* to DOCKER_AGENT_* while maintaining backward compatibility. The implementation correctly implements a fallback chain (new env var → old env var → config file) for both MODELS_GATEWAY and DEFAULT_MODEL.

Changes reviewed:

• ✅ Backward compatibility fallback logic added in cmd/root/flags.go
• ✅ Tests updated to use new environment variable names
• ✅ Container evaluation logic updated in pkg/evaluation/eval.go
• ✅ Task file updated for test commands

Note: While the implementation is correct, the test suite could be enhanced by adding explicit test cases that verify the backward compatibility fallback (setting only CAGENT_* variables without DOCKER_AGENT_*). This would ensure the fallback mechanism continues to work in future refactorings.

Findings

No critical or notable issues found in the changed code.

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Review performed by cagent PR review bot