A Sterile-Neutrino X-ray Target from the Finite-QEC Dark Sector: m_nuR = 17.68 keV, E_gamma = 8.84 keV

A Sterile-Neutrino X-ray Target from the Finite-QEC Dark Sector: m_nuR = 17.68 keV, E_gamma = 8.84 keV. A dated pre-registration note recording the finite-QEC framework's sterile-neutrino dark-matter X-ray target, in the same style as the dark-energy w0,wa note. The sterile state is the passive nu_R of the record code, with mass m_nuR = alpha0^2 Lambda_QCD ~ 17.7 keV, so its radiative two-body decay nu_R -> nu + gamma gives a line at E_gamma = m/2 ~ 8.84 keV (NOT the 3.5 keV line, which would need a ~7 keV sterile). The line energy scales linearly with Lambda_QCD and its scheme/flavour-number choice is the dominant uncertainty, so the honest target is ~8.8 keV within a few-percent window under a stated Lambda_QCD convention, not a sub-eV bin. A conditional abundance from the boot-QEC source law n_nuR/n_gamma = alpha0/208 gives Omega_nuR h^2 = 0.0242, and with a 4:1 paired zero-mode reservoir Omega_dark h^2 = 0.121 (matching the observed cold-dark-matter density; a postdiction). In the named one-denominator R4-enforcement branch the active-sterile mixing is fixed at sin^2(2theta) = 2.1e-14, giving a faint line (lifetime ~2e32 s) below near-term XRISM and probably below even Athena reach, so the flux is a long-term test; the robust near-term content is the line position and the prediction of no bright line at that energy. Targets are staged by tier: energy and abundance are sharp conditional targets, flux is a conditional prediction inside the named R4 branch. Companion to the dark-energy prediction note and the finite-QEC dark-sector work. This record is part of the finite-QEC substrate / It-from-Bit publication refresh.