What is the name of the "agency" fallacy?

To propose it formally then: Pathetic fallacy, the "the attributing of human emotion and conduct to all aspects within nature. It is a kind of personification that is found in poetic writing when, for example, clouds seem sullen, when leaves dance, when dogs laugh, or when rocks seem indifferent."

Also somewhat strangely referred to as "anthropomorphic fallacy" (which is not a fallacy shaped like a human as one might expect), as it comes about from anthropomorphism (personification), i.e. attributing human features to non-human entities, which is commonly done spontaneously as basis of most mythologies, and intentionally as a literary device.

Also note that, unlike the standard literary definition found in most sources as well as the Wikipedia quote above, I personally would not call "magnets are trying to avoid each other" a fallacy in most cases, but rather a colorful and memorable description of the phenomenon, and either of the neutral terms "personification" or "anthropomorphism" would fit the situation much better. It only becomes a fallacy when one uses the attributed emotion specifically as a premise for (faulty) logical reasoning. ("magnets are trying to avoid each other? so if we ask them very nicely they might stop?")

The fallacy is called the agency fallacy.

I first came across the agency fallacy in a series of audio lectures on evolutionary psychology by Allen MacNeill ('Evolutionary psychology' from 'The Great Courses' audio series available for download on Audible). I'm pretty sure Ben Shermer references it in his book 'Why people believe weird things' too.

As an aside, The blog you linked to was my own.

As others have rightly pointed out, this isn't strictly a fallacy unless used as the premise for an argument--typically, it's more like a bias. Searching Google for "agency bias" yields much better results, including multiple academic articles such as this one. "Agency bias" or "bias toward agency" appears to be the accepted term.

Perhaps in cases where this bias is used in an argument (such as with the example of the socialist on a soapbox), it might informally be called the agency bias fallacy, or simply the agency fallacy.