Please help me identify this plant

Something self-seeded in my raised-bed garden. This is in Minnesota if that helps.

Here’s the whole plant.

This is one of the big, heart-shaped leaf.

Here is a bud and a seed pod. The seed pod is the thing right next to my thumb.

What is this?? And does anyone have any idea how it would have gotten into my garden? I only put out sunflower and safflower seeds for the birds, and it doesn’t appear to be either of those, but I suppose a bird could have brought it in from somewhere else and “deposited” it. Other ideas?

It’s a species of mallow. Or a plant of the mallow family.

Surely a seed mixed with the sunflower seeds.

Indian Mallow