setTextFieldValue

Fill a text form field: set its value (/V) and regenerate the widget's normal appearance (/AP /N) so the value is visible in any viewer. The appearance honours the field's /DA (font, size, colour) and is clipped to the field rectangle. Also clears the form's /NeedAppearances flag (if set) so viewers use the appearance we just generated.

Only /Tx (text) fields are supported; buttons/choices come later.