кра/j/eуго́льный phonemically.
But it’ş commonly pronounced as кра[и]уго́льный without the [j] sound or with a very weak one (like other unstressed је’s).

кра[э]угольный is definitely wrong.
«Е» after a vowel is pronounced like [э] only in the word проект. (I have no idea why. The latin ancestor does have a ‘j’ in it).