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The Thirteenth Amendment to the US Constitution provides (my emphasis):

Section 1. Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.

Section 2. Congress shall have power to enforce this article by appropriate legislation.

This clause seems to indicate that the legal status of chattel slave whose use had triggered the passage of this amendment was not fully abolished by it, but that this form of slavery could be imposed upon criminals as part of their sentence.

Did this ever happen?

I am very much aware of human rights issues surrounding the use or abuse of prison labor by governmental agencies and private correctional companies. This quesiton is not about that, but about true, pre-Civil War-type chattel slavery. That is, did a court ever tell a defendant something like, "We find you guilty of Second Degree Aggravated Mopery with Intent to Do This and the Other Bad Thing, Third Offense. You are hereby sentenced to a life of chattel slavery and shall be auctioned off in the town square at high noon tomorrow."?

Yes, but for fixed periods of (for example) six months or 1 or 2 years rather than for life. This section of the 13th Amendment, ratified on the 6th of December, 1865, was controversial from the outset. Slavery Under the Thirteenth Amendment: Race and the Law of Crime and Punishment in the PostCivil
War South by Peter Wallenstein in the Louisiana Law Review (vol 77, No. 1) has this example from Maryland of the punishment of slavery being imposed:

On December 8, 1866, in Annapolis, Maryland, a crowd gathered at the
county courthouse for an auction. A recent advertisement in the
Annapolis Gazette had called the public’s attention to the upcoming
event with the language “Public Sale . . . a Negro man named Richard
Harris, for six months, convicted at the October term, 1866 of the
Anne Arundel County Circuit Court for larceny and sentenced by the
court to be sold as a slave. Terms of sale—cash.”

Public domain, from unpublished congressional digest. Source: The inseparability of capitalism, racism, and imprisonment: an interview with Dennis Childs

Other examples mentioned (all black, unsurprisingly):

Continuing after ratification, a series of announcements later that
month called for sales of other people, among them “a negro man named
John Johnson . . . sentenced to be sold” for one year; “a negro man .
. . named Gassaway Price . . . to be sold for a term of one year”; “a
negro woman . . . named Harriet Purdy . . . to be sold for a term of
one year”; and “a negro woman . . . named Dilly Harris . . . to be
sold for a term of two years.” The charge originally brought against
each of these five people— called “larceny” in the advertisement
although it was actually “petit larceny”—specified the theft of a hog,
for example, or of a bushel and a half of wheat. For the services of
Harriet Purdy for a year, for her alleged theft of a pair of boots, a
white man named Elijah Rockhold paid $34

The sentence was not for life but rather for a number of years.

Whether before or after the “end” of slavery, these “slaves” were not
to be held in perpetuity, but for a period of years. Even after all
black Marylanders had moved into the category of free people, the
statute lost none of its ferocity, nor did it shed its racial
specificity. These circumstances could exist because the Thirteenth
Amendment expressly allowed state actions such as those taken by
Maryland authorities.

Abuses appear to have been widespread, with Republicans at the time protesting that, although the letter of law was clear, the spirit of the law abolishing slavery was being "avoided and got around by these cunning rebels."

In 1866, many Republicans complained that former Confederates were
abusing the crime exception to impose slavery even for minor
crimes....Representative Henry Deming complained, “[U]nder the
exceptional clause (‘except as a punishment for crime’) reconstructed
North Carolina is now selling black men into slavery for petty larceny
. . . .”

Your question is trying to be so precise that it embeds its own answer. You ask:

This quesiton is not about [the human rights abuse that is convict leasing], but about true, pre-Civil War-type chattel slavery. That is, did a court ever tell a defendant something like, "We find you guilty of Second Degree Aggravated Mopery with Intent to Do This and the Other Bad Thing, Third Offense. You are hereby sentenced to a life of chattel slavery and shall be auctioned off in the town square at high noon tomorrow."?

However, one of the salient features of chattel slavery in the US was that it was an inherited condition--any child born to an enslaved mother would be enslaved themselves. But enslaving the child would be a violation of the 13th Amendment. Therefore it would not be possible to recreate an exact replica of antebellum chattel slavery, even if you bound someone to "involuntary servitude" for life, because even someone enslaved through that loophole would not pass that status to their children.

That said, I think you're parsing this too finely. When you have no rights to withhold your labor, a three-year sentence can easily be a life sentence if whoever purchases/rents you sets you to sufficiently dangerous work. Or decides to move you across the country. Or provides so inadequately for your welfare/withholds medical attention from you such that you die during your term. All of which are ongoing processes in present-day prisons in the US. There are too many potential actions which render the distinction between de jure antebellum-style chattel slavery, and the abuses which continue in the US every day today, irrelevant.