feat: add versioned NDJSON streaming output

[codeforester]

Summary

• add bounded, flush-per-record ndjson output
• define stable schema/version fields and typed writer protocols
• preserve existing JSON, CSV, TSV, YAML, and human output behavior
• document stream/error boundaries and add regression coverage

Validation

• python -m pytest (all tests passed)
• ruff check and ruff format --check
• python -m mypy --strict lib/python/base_cli
• scripts/validate_docs.py
• ./tests/validate.sh
• git diff --check

Closes #192