Degree-staircase emergence is architecture-shaped, while optimizers shift only its timing

Code and result logs showing the degree-staircase of sequential feature acquisition is owned by depth and attention. Code is MIT; result logs CC-BY-4.0. Figure/manuscript sources not included; large standard datasets not bundled. v1.2 adds the degree-5 staircase extension and isolated-parity control logs and the optimizer-axis analyzers reported in the submitted manuscript. v1.3 adds the 24-configuration scale grid and the 8-seed freeze-ownership audit (runner + 144 result logs) reported in the submitted manuscript.