As long as no video was recorded no rules were broken. It’s not the Seahawk’s fault Manning became predictable.
From the descriptions of the process, Denver must have been exceptionally clueless Sunday. They spent the first half watching the signals, and calling out their predictions, before settling on the meaning somewhere in the second half. They had to hear some of that, or notice something was up. Seattle had shut down Denver’s offense fairly well before that point, so I doubt it made a whole lot of difference until the substitutes started to play.
Manning’s codes probably weren’t too difficult to figure out. I recall when they played Dallas earlier this year, every time he yelled an animal name like, “jaguar” or “cheetah” it switched to a run play. It’s brute force, not rocket science.