Massive free-shell tangency

This is a local classification in a developing chart CheungIIIKilling. It does not assert that every local Poincare generator extends through conical holonomy. No massless version is inferred.

The distinction from Theorem thm:product is essential: that theorem fixes $\varphi$ and changes only its metric representative. The present theorem tests whether moving $\varphi$ preserves its unchanged equation.