Invalid shortcuts and their exact logical boundaries

This is the limited reason collision contacts cannot, merely by being added, repair a missing characteristic operation on a neighborhood disjoint from those collisions.

The coverage account records further boundaries record:

1. an exact smooth-slot identity is not a joint-symbol theorem;

2. a common phase that fails clean or nondegenerate hypotheses does not become valid by being renamed;

3. a rank discrepancy is not automatically composition excess;

4. individual symbol descriptions do not define a joint product;

5. smooth residual testing can remove attachment-diagonal wavefront information;

6. a branch diagnostic is not a cancellation theorem for the entire six-branch sum.

The detailed phase, rank, and tangent calculations are not reproduced here. XV-A uses these as reported exclusions of particular shortcuts, not as newly proved universal obstructions.