D8: Nambu 3-bracket (difference approximation) — skeleton

We introduce a minimal interface for a family of difference-derivation operators L_i (i=1,2,3), a placeholder Nambu bracket built from them, and a Fundamental Identity (FI) error bound stated as a Prop over an intended domain (e.g. H_σ ∩ H^2_× from design). No heavy analysis here.

@[reducible, inline]

abbrev Frourio.Func : Type

Equations

• Frourio.Func = (ℝ → ℂ)

@[reducible, inline]

abbrev Frourio.DiffOp : Type

Equations

• Frourio.DiffOp = (Frourio.Func → Frourio.Func)

structure Frourio.DiffFamily : Type

Family of three difference derivations with light metadata.

• L : Fin 3 → DiffOp
• commute : Prop
• smallParams : Prop