fix: reset canvas transform before clearing to prevent rendering artifacts

[Antamansid]

CanvasApi.clear() used clearRect without resetting the canvas transform to identity first. When external code (e.g. Events.setSelectedEvents()) called render() directly outside of the rerender() cycle, it left a dirty scroll transform on the canvas context. On the next rerender(), clearRect operated in the transformed coordinate space — and with a large canvasScrollTop, the clear area shifted entirely above the visible canvas, resulting in nothing being cleared. Subsequent component renders drew on top of stale content, producing visual ghosting artifacts.

The fix resets the transform to identity (1, 0, 0, 1, 0, 0) before clearRect, ensuring the full physical canvas is always cleared regardless of any residual transform state.

[gravity-ui-bot]

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