Add shared basectl output-format renderer

[codeforester]

Summary

• add shared TTY-aware text, CSV, TSV, YAML, and JSON rendering helpers
• keep delimited output headerless and diagnostics separate from stdout
• document the shared contract and cover resolution, quoting, empty output, and structured serialization

Validation

• focused output pytest
• base_cli unittest suite
• git diff --check

Closes #1692