test_update_nixpkgs_inputs: TestDiscoverInputs flake_lock test fails on main (root + pkgs/id copies) #5725

Problem

TestDiscoverInputs.test_current_flake_lock_keeps_the_four_intended_inputs in scripts/tests/test_update_nixpkgs_inputs.py fails on clean main (verified 2026-11-05 on laptop primary at 03032fd, and identically on a task worktree based on the same commit):

• FAIL (copy='root')
• FAIL (copy='pkgs/id')

python3 -m unittest discover -s scripts/tests -p "test_update_nixpkgs_inputs.py" → Ran 14 tests, FAILED (failures=2). The other 12 tests pass; the cold-store suite is unaffected.

This looks like flake.lock input drift: the current lock no longer matches the four inputs the test asserts. Either the lock legitimately gained/lost an input (test expectation is stale) or an input was dropped/added unintentionally (lock is wrong).

Found during

Queue task 9769 / issue #5712 (moving mid-file unittest.main() guards) — the failure is pre-existing on clean main and unrelated to that change; discover outcome before and after is identical (14 tests, same 2 failures).

Acceptance

• Determine whether the flake.lock state or the test expectation is correct.
• Fix whichever is wrong so the test passes on main.