fix(canvas): stop hardcoding inline CSS size on the output canvas

renderDiffToCanvas set canvas.style.width/height to the fixed
1200x675 social-share default. Inline styles win over the stylesheet's
responsive `width: 100%` rule, so every generated image forced the
card past the viewport on phones and tablets. Sizing the pixel buffer
(canvas.width/height) is enough for DPR-crisp rendering; display size
is the stylesheet's job.

Author: ctkrug

src/render/canvas.js

@@ -52,8 +52,6 @@ export function renderDiffToCanvas(canvas, segments, options = {}) {
 
   canvas.width = Math.round(width * dpr);
   canvas.height = Math.round(height * dpr);
-  canvas.style.width = `${width}px`;
-  canvas.style.height = `${height}px`;
 
   const ctx = canvas.getContext("2d");
   ctx.setTransform(dpr, 0, 0, dpr, 0, 0);