Is squirrels feeding on nuts from a tree predation?

No predation is when a predator gets its nutrition form another animal.
Think of lions and wolves.

it would be commensalism, where one organism benefits and one is unharmed.

Squirrels, and rodents in general, are considered seed predators. Typically predators are defined as killing and consuming prey. Squirrels do kill the seed, a potential plant, but they do not kill actual rooted plants so they earn the qualified epithet: seed predator.

Plants have adapted to rodents, like squirrels, that hide seeds in scattered hoards.  The plants produce seed in sufficient numbers to offset what the seed eaters consume and in turn rely on the rodents forgetting some seed caches.  In this way the squirrel is simply a well paid employee dispersing the seeds. Plants and animals that disperse seeds are considered to be in mutual symbiosis.

While the squirrels do harm to the tree by taking a portion of its reproductive efforts they do not kill the tree nor, in most cases, prevent it from reproducing.