Generic kinase / phosphatase reversible-phosphorylation toggle motif

The minimal, reusable reversible-phosphorylation switch: a protein kinase phosphorylates a substrate to set one functional state, and an opposing protein phosphatase removes the phosphate to reset it. This antagonistic kinase/ phosphatase pair acting on a shared substrate is the most pervasive regulatory toggle in biology (cell-cycle CDK/phosphatase pairs, the DUSP/MKP feedback in MAPK cascades, receptor kinase/phosphatase balance, etc.). The motif is gene-free and taxon-neutral: it fixes only the kinase and phosphatase roles by molecular-function term and their opposing action on one substrate state. Concrete switches embed it through `conforms_to`, substituting their own kinase, phosphatase, and substrate. Grounded in GO:0006468 (protein phosphorylation) and GO:0006470 (protein dephosphorylation).

Reusable conformance target. A node declares `conforms_to: [{template: kinase_phosphatase_toggle}]` when a kinase and an opposing phosphatase set and reset a shared substrate phospho-state. The direction of the regulation (whether phosphorylation activates or inhibits the substrate) is realization-specific and recorded on the concrete module.