- README: add YAML config section, --by-activity, bare format --output, output without extension, period.precision - CONFIG: document period.last_used, period.precision (date/datetime), output path resolution rules, resolve_output_path() behavior
- README: add YAML config section, --by-activity, bare format --output, output without extension, period.precision - CONFIG: document period.last_used, period.precision (date/datetime), output path resolution rules, resolve_output_path() behavior