I think 'Tenet' means 'Travel Net', perhaps 'Time Travel Net'
In the trailer, the main character says 'I only have a word for you: tenet'
We don't know whether the spelling is correct. Perhaps he just heard it and he's misspelling it. Perhaps it's not 'Tenet' but 'T-Net'.
'T-Net' can be an acronym for Training Net, or Transport Net, or Travel Net (or Time Net, maybe?). This movie includes time travel, so T-Net could refer to some kind of Time Travel Net or Time Transport Net.