Ruler for turtle canvas for x and y axes

FAO: Marie Roald and Yngve Mardal Moe

I use graph paper to do designs in turtle. The smallest square on graph paper is 2mm squared, this is the equivalent of 10 turtle steps. The numbers work with the y-axis (0,230) to (0,-230) and the x-axis (-620,0) to (620,0). The visual output on the turtle canvas is scaled down by a ratio of 2:1. To mimic how the design looks on the graph paper is challenging, so I use a square that is 5ts squared (turtle steps). The canvas image is understandably smaller but for complex designs (e.g. Celtic Knots) the turtle output accurately displays the design at that scale.
FYI,
Turtle Demo examples are used in high schools (secondary schools) all over the United Kingdom but only to change a line of code to see the effect (usually the color string). If a ruler were added this might result in greater use of turtle. Additionally, the turtle specification (Python Docs) and the color strings are not well-known in the classrooms. This too is a hindrance to future use of turtle. Consider what is on Instagram regarding turtle.
Finally, the canvas scale needs to be altered because the solution to a Pythagoras Theorem (c2=a2+b**2) cannot be displayed correctly in the turtle canvas. The points will not connect to create a right-angled triangle.

Start by narrowing the request to the turtle canvas ruler, canvas scaling, or documentation, since the issue combines several separate goals. Define the expected axes, scale, and visual behavior with concrete examples, then identify the turtle canvas entry point and tests needed to verify the selected change.