A genuine linear free-shell quantum repair

This is the linear repair of VII-B, now with its free algebra consequence made explicit CheungVIIB. It changes off-shell equality to free-shell equality.

For the bilinear insertion the test $a=f\mathrm{d}\varphi$ depends on the quantum scalar field. Applying a linear repair separately at each fixed $\varphi$ does not prove a joint microcausal kernel, compatibility with contractions, or interacting equation-of-motion identities. Those obligations remain.