Fixed mode preregistration for future KNTW LO-HVP window combinations

This registration freezes a fixed-mode prediction for future KNTW style data driven LO-HVP window combinations in the shared (ID,FULL) Euclidean-window subspace. The operative preregistration is the attached document 'fixed_mode_preregistration_v1.pdf', mirrored by 'fixed_mode_preregistralion_v1.md'. It locks the window basis, branch definitions, sign convention, primary predictions, confirmation and falsification thresholds, secondary rho-band localization prediction, and negative control conditions. The registration is prospective relative to any future unblinded KNTW release used as the text object. Its purpose is to timestamp the prediction before such future results are inspected or incorporated. Related Zenodo release: 10.5281/zenodo.20279233