When I installed linux-headers-amd64, the dkms process built the modules as expected, and now my machine is back up with graphics.
It appears that the bug is that linux-headers-amd64 needs to be a dependency of nvidia-driver.
- Bug#1079591: nvidia-driver: Installing nvidia-driver in sid... Forrest Cahoon
- Bug#1079591: Issue resolved by installing linux-header... Forrest Cahoon
