B0: audit of the supplied XII-A handoff

The supplied predecessor is XII-A-v2.tex, cited here as XII-A XIIA. Its actual release is a polynomial-carrier construction for the frozen XI-track multiplet. It includes:

• the separation of equation geometry from action normalization;

• a regular quantum presentation and a shell quotient;

• a smoothing-based descent argument;

• ordering transport and the named composite sector;

• delimited continuity statements;

• robustness of the detected observation class;

• a regular ambient–slab identification.

These are relevant algebraic prerequisites. They are not a definition of a new cubic action.