1) In the aggregates, 'sankhara' are kammic formations.
Yes. Sankhara creates future results. So karmaic results are due to Sankhara. Sankhara is like the seed which germinates into the result.
2) Kammic formations are any phenomena that have an underlying intention, and therefore create new kamma.
Intention decides which of the 121/89 mind states arise. Each mind has The 52 Mental Factors (cetasika). Out of the 52, 50 are Sankhara which results in conditioning future experiences which are also known as karmic results.
Question: Is intention (cetana) a sankhara?
Cetana is a part of sankhara, which is 1 part out of 50 mental factors. There are 49 other factors which are considered sankhara. Cetasika has sanna and vedana also, excluding these factors the rest is sankhara out of which Cetana is one factor. As cetana is a Universal mental factor this always arising with the rest of the mental factors pertaining to a mind-state.
Cetana is also part of the phenomenon triggered by contact, as all minds arise with contact. With each mind-state all factors pertaining to vedana, sanna and sankhara arise out of which cetana is one factor.
Centana decides the wholesomeness or unwholesomeness of the mind and sankhara creates. E.g. For a positive mind, 14 of the Unwholesome mental factors will be missing. These 14 are sankhara which gives bad results.