Can they dug and graded and parked right next to my tree during the build, and now it looks bad be fixed without removing the tree?

Frequently, and the decision turns on how much root area was lost and where. Roots cut on one side only, close to the trunk on that side, is the worst case for both survival and stability. What genuinely helps: deep irrigation through every dry spell for at least the next two or three growing seasons, wide thin mulch over the root zone, compaction relief with an air tool or vertical mulching rather than tilling, and nothing else that adds stress. What does not help, despite still being sold: crown reduction 'to balance the roots' — a damaged tree needs its leaves to rebuild roots — plus heavy nitrogen fertilizer and injections. Removal is right when roughly half or more of the root plate was destroyed, when the tree has begun to lean or the soil has cracked opposite the cutting, or when it stands over the new house. The most valuable thing an arborist can do is arrive before the excavator: protective fencing at a tree protection zone, commonly set with a rule of thumb of one foot of radius per inch of trunk diameter, costs almost nothing against what it saves.