Add nix service definition for codex #4147

Job	Run time
matrix	19s
coverage	6m 41s
build / linux-unittest-amd64-pinned	6m 7s
build / linux-contract-amd64-pinned	6m 11s
build / linux-integration-amd64-pinned	6m 10s
build / linux-tools-amd64-pinned	6m 7s
build / macos-unittest-amd64-pinned	6m 8s
build / macos-contract-amd64-pinned	6m 10s
build / macos-integration-amd64-pinned	5m 58s
build / macos-tools-amd64-pinned	6m 10s
build / windows-unittest-amd64-pinned	6m 8s
build / windows-contract-amd64-pinned	6m 12s
build / windows-integration-amd64-pinned	6m 6s
build / windows-tools-amd64-pinned	6m 8s
build / status	1s
	1h 20m 36s

Provide feedback