v0.5.3

Added

• CurveEditor widget for editing chart-space knots with D3 curve interpolators. Open curves store points in x order, while closed curves preserve drawing order so double-clicked points are appended to the loop. Curves can render with linear, step, basis, natural, cardinal, Catmull-Rom, monotone-x, and bump-x curves. A bottom progress control emits t, x, and y from the rendered path, with optional closed-path and loop playback controls.
• BezierCurve widget for editing arbitrary-degree Bezier curves in notebooks. Drag control points, double-click to add points, optionally close the curve, and play through t with loop-aware playback.