refactor tests to avoid atmos binary

[osterman]

trafficstars

what

• run test cases via cmd.Execute() instead of compiled binary
• update terraform CLI tests to use helper
• fix golangci configuration for lint
• document in-process test execution
• clarify lint instructions in AGENTS.md
• disable timestamp in logs for in-process test helper

why

• executing the compiled binary in tests caused flakiness and reliance on external artifacts
• running commands in-process provides faster, more reliable testing
• lint required --new=false since the container isn't a full git repo
• log timestamps broke golden snapshots

references

• n/a

---

https://chatgpt.com/codex/tasks/task_b_68597d71f1c48332971e1760f706d4b8

[mergify[bot]]

[!WARNING]

This PR exceeds the recommended limit of 1,000 lines.

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Please verify that this PR does not address multiple issues. Consider refactoring it into smaller, more focused PRs to facilitate a smoother review process.

[mergify[bot]]

[!IMPORTANT]

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[mergify[bot]]

💥 This pull request now has conflicts. Could you fix it @osterman? 🙏

[osterman]

superseded by #1534