Synthetic Chevron repeat exercise

Start with the built-in Chevron repeat, or Open... the supplied
examples/frigella/chevron-repeat.frigella.json. The default PDF is two pages:
one chart and one legend, 20 stitches × 12 rows, colours Moss and Oat.
In PDF settings choose Fixed cell size and Cell height 30 pt. The page plan
changes to two chart pages plus one legend page. Compare chevron-tiled.pdf.
Switch back to Fit the chart on one page. Choose black and white and untick
Print symbols in the cells: read the blank-cell warning. Restore symbols
before downloading a monochrome chart. Save the editable project separately.
These are chart-planning examples, not physically validated knitting patterns.
