SVG 渲染: linearGradient 填充显示为黑色, text-anchor 并未从祖先元素继承

1. linearGradient renders as solid black

A rectangle with fill="url(#bg)", referencing a valid linearGradient, renders solid black instead of the expected light blue-to-green gradient. At the center of the rectangle, the rendered RGB value is (0, 0, 0) in MuPDF and (241, 250, 250) in librsvg.