refactor(import[argparse]) Rename output argument group to reflect behavioral flags

[tony]

The `output` argument group in `_create_shared_parent()` (`_common.py:241`) contains mutation/behavioral flags (`--overwrite`, `--yes`, `--dry-run`, `--https`) alongside output format flags (`--json`, `--color`).

The name "output" is misleading for flags that govern config mutation.

Suggested fix:

• Rename to "Output and behavior" or split into separate groups

Found by multi-model code review (Gemini, 1/3 consensus). Finding #6.