OpenTUI QR Code

@opentui/qrcode includes a QR Code Model 2 encoder and a renderable for OpenTUI.

The renderable uses half-block cells to keep the symbol square in terminal cell geometry. React apps call registerQRCode() once and then use <qr-code>. Solid apps call registerQRCode() once and then use <qr_code>.

The encoder APIs produce matrices or serialized output. They do not require a mounted renderable.

Read the QR code component, QR encoder, and package entry points.