I have been thinking about this a bunch recently and researching it a bit, both without good effect

I mean the observer effect, not the towel. 

I could use a little guidance 

What counts as observation? How does it play out if you make a cat observe? A fly? A camcorder? Is the effect binary or can some kinds of weak observation create semi-wave-semi-particle behavior?

Assume I am clueless on the subject but will be able to carry myself forward with a curated list of articles or search terms

You are misinterpreting what the term "observer" means in quantum physics. In the double-slit experiment, the observer effect is not about human or animal observation. It doesn't matter if a person, a cat, or even your ficus plant looks at the result. The crucial point is whether there's a measurement or interaction that determines which slit the photon passes through.

When the photon travels freely (unmeasured), it behaves as a wave and interferes with itself, creating an interference pattern. However, the moment you introduce a measurement device or sensor at the slits to determine through which slit the photon passes, this interaction collapses its wavefunction. This act of measurement, rather than the presence of the slits or a passive screen, is what is an "observation" in quantum mechanics and causes the loss of the interference pattern.

Ok, so consciousness is not the issue. 

But what does measurement mean? What kinds of non-measurement interactions cause the collapse? How does a particle know it’s being measured?

OK, now we’re getting somewhere. Thank you for your patience. 

> This interacts as it slightly makes the photon be "attracted" by the field measurement tool.

This makes more sense. What is the mechanism of attraction, though? And would a non-observing object of otherwise equal character have the same effect?

> Measurement means any mean that allows you to know for sure the photon has passed one slit and not the other.

I’m sure that “know” is shorthand here, but “know” makes it sound again like awareness matters. But the whole point, I think, is that any outcome-dependent interaction with the photon that’s close enough to the slit will collapse the wave into particle behavior. 

Even dumber question: does the photon just die when it hits the foil? What if there’s no foil? Does it just carry on as a particle for the rest of its existence? Does it revert back to wave at some point?

For instance for a photon, measurement of the electromagnetic field variation at the slit can tell what slit was passed. This interacts as it slightly makes the photon be "attracted" by the field measurement tool. If you put a camera in place of the slit, it's even more obvious as it prevents the photon to pass the slit and it's blocked by the camera sensor. But even non blocking measurement collapses the wavelength.
Measurement means any mean that allows you to know for sure the photon has passed one slit and not the other. The screen behind the slits for instance is not a measurement because it's too far away and doesn't make you sure what slit was passed. So your wavelength is still intact and interference appears on the screen.

As for the non measurement, think of measurement as anything that allows to know what slit is passed even if it's non intentional. It may be things like scattering if the photon passes through some medium and interacts with molecules in a way that, if it was measured, would reveal the slit passed. There's many clever ways to know what path the photon took and even some that we don't really know how to measure.