AcDbDxfPair:
| { code: number; type: "string"; value: string }
| { code: number; type: "int"; value: number }
| { code: number; type: "long"; value: number | bigint }
| { code: number; type: "double"; value: number }
| { code: number; type: "bool"; value: boolean }
| { code: number; type: "handle"; value: string }
| { code: number; type: "binary"; value: Uint8Array }
One typed (group code, value) pair from a DXF tag stream.
Both ASCII and binary readers produce this shape so consumers stay format-agnostic. Handles stay as hex strings to match AcDbObjectId.