Does measurement have to include an agent? Could measurement mean interaction with other atoms?
Indeed it can. Roughly put, if information about the state left the undetermined system, a measurement has been made. One of the most frustrating interpretations of literature such as this is the idea that there is something spooky, special, and reality-making about a conscious mind. Lots to think about there philosophically, but the physics happens at lower levels of abstraction.
Personally, I think the simpler and less egocentric view is that all measurements produce wavefunction collapse, even when there's nobody looking.
See https://en.wikipedia.org/wiki/Von_Neumann–Wigner_interpretat... and https://en.wikipedia.org/wiki/Measurement_problem if you want to read more.