getPackedExtendedAttr
Returns the extended packed attribute word for the cell at col.
The extended word stores underline color/style, decoration flags, conceal, and the numeric hyperlink id. Renderers should read it together with getPackedAttr and decode both words with io.github.ketraterm.core.codec.AttributeCodec.
This method is intended for render loops and performs no allocation.
Return
Extended packed attribute word for the cell.
Parameters
col
Column index (0-based).