L.2 Complete graph decomposition

The graph has the four pieces of XVI-K, Section K.2: source point $y$; interaction point $w$; root $B_{f,g}(y,x)$, attached only in the target L.7; scalar test $\varphi (x)$. Both edges run from $y$ to $w$. Each edge carries $D_F(y,w)=-\mathcal{P}S(y-w)$, with $S$ of XVI-K, eq:S; the factor $-\mathcal{P}$ acts on tensor indices and $S$ is the scalar numerical part. The change relative to XVI-K is that the source end is the complete polarized source ${\mathfrak{s}}_A$ of Definition def:sA, $A\in \{C_2,M_2,J_3\}$, rather than the $C_2$ summand alone.