My advice from dealing with this issue over the years but also not a tree expert by any means. What I have been told is that it can take several years for the damage to show up. That being said, things aren't necessarily that fragile but it depends a lot on the tree.

There is a 50 yo Oak just behind our rear property line. This is a tear down area. and the house behind got built just before we bought out lot. They did a rear/side entry garage and built at the 30 feet line from the rear - 25 feet from the tree. Then we built with a rear entry garage - also 30 feet back with 22 feet or so of driveway - 30 ft wide - ending just past the trunk. So we covered almost 25% of its roots, A fence was also built at the property line - 2 feet from the trunk.

Our rear neighbors just built a concrete patio with a fire pit in the drip line - but on the periphery.

The tree looks fine and we have been in 2 years. I would not bet money the tree will survive but it looks perfectly fine.

I should mention that I also planted several large things in the dripline.

5-10 years is usually the time line for damage to show up.

Don't expect anything less in California where we typically have to install temporary fencing around driplines of protected trees (mostly Valley & Blue Oaks) & in some jurisdictions monitor & maintain under a licensed arborist's watch.

Excavation may be done but there's still lots of activity to come and it's not too late, get some construction fencing and stakes and protect the dripline. If it wasn't called for in your contract then it's your dime. If for some reason you can't surround the dripline, then strapping around the trunk to protect that, but be aware that prolonged exhaust from say a skid steer doing final grading under the tree can kill a low branch.