/line

Generate a line chart with grayscale styling for academic publications

## Goal

Generate a publication-ready line chart with grayscale styling and Chinese font support.

## Preparation

Collect the following parameters from the user:

| Parameter | Required | Default | Description |
|-----------|----------|---------|-------------|
| `data` | Yes | - | Data source: CSV file path, or inline data |
| `x` | Yes | - | Column name for X-axis |
| `y` | Yes | - | Column name(s) for Y-axis (comma-separated for multiple lines) |
| `group` | No | - | Column name for grouping/coloring lines |
| `title` | No | - | Chart title |
| `xlabel` | No | X column name | X-axis labe...