"It doesn't exist". Well! The difference between the intent of the law and the "letter" of the law: The Constitution, if it is about anything, it is about Balance of Power.
Since it accepts slavery in its original form the "intent" as you put it is probably not acceptable to you. Unless of course you spend your weekends with a pillowcase on your head.
An afterthought? No. The Constitution was a document provided at the behest of the States, with their approval (not dictated by the Feds), and those States would not ratify said document without the Enumeration of rights now referred to as the Bill of Rights.
Actually there was a long and protracted debate over whether or not to include the bill of rights in the constitution. A constitution is simply a description of the process and organisation of government, usually in the broadest terms. The problem with the bill of rights at the time of the discuissions was enforcement. The role of the supreme court as arbiter of the constitution was not originally planned. If anyone had predicted that such a role would emerge it would have been seen as undesirable since it would compromise the judicial/legislative separation. Incidentally one of the original gripes of the revolution was the type of recourse to unwritten proceedure and laws that happened in the colonial period. That is why there was a demand for a clear statement of the constitutional arrangements. If jefferson and so wanted private kangeroo courts they would have written it down. Phill