Coarse-graining support: Support.CoarseGraining.ResponseIdentities.Foundations

Imported from the Apache-2.0 CoarseGraining development at commit c7ddd76c08ade64fed1b8d2ca51be14dfee8deb4.

Foundational scalar deterministic identities for ResponseJ (aggregate)

Historically a single monolithic file; now split along namespace/section boundaries into the three modules imported above. This shim re-exports everything so downstream consumers keep working unchanged.