Deposition-Sink

Operator model that turns first-order dry + wet deposition loss-rate coefficients into additive sink terms on a SuperFast-family gas-phase mechanism. Each equation is D(<X>) ~ -(k_dry + k_wet)*<X> over the model's OWN species unknowns; when this model is merged with a SuperFast reaction system via an `operator_compose` coupling (systems: [<Chem>, SuperFastDepositionSink]), the flattener matches each sink equation's dependent variable to the chemistry system's state of the same species name and sums the two right-hand sides (dc/dt += -k*c), then retires the sink's own declaration of that name (esm-spec 10.1/10.2 — direct match, else the bare-name match). The deposition rate coefficients are exposed as parameters so they can be driven from the full DryDepositionGas (Wesley 1989) and WetDeposition (EMEP) components via param_to_var edges in an assembly. Species->rate mapping mirrors AtmosphericDeposition.jl/ext/GasChemExt.jl couple2(SuperFastCoupler, DryDepositionGasCoupler / WetDepositionCoupler): NO reuses NO2's dry-dep rate; CH2O uses the formaldehyde (HCHO) dry-dep rate; the wet rate k_wet is the lumped soluble-gas WetDeposition.k_othergas applied to HNO3, H2O2, CH2O, CH3OOH.