[zzoraemon043]

Description

math.smoothstep and math.smootherstep returned early on x <= min / x >= max, which only works when min < max. With reversed edges they became an inverted hard step at min. They now clamp the normalized value to [0, 1] before the polynomial, the same as GLSL, so reversed edges give a falling ramp. When min === max the result stays a step (0 at or below, 1 above), as before, instead of dividing by zero. The min / max docs now say which value maps to 0 and 1.

Added tests for clamping, reversed edges (including the values from the issue) and equal edges.

Fixes #9767

Checklist

• I have read the contributing guidelines
• My code follows the project's coding standards
• This PR focuses on a single change