neural_reversible: a register machine whose entire state transition is a bijection. Reversible threshold gates (CNOT/Toffoli/Fredkin as Heaviside AND/XOR), a reversible ALU (Cuccaro in-place adder, subtract as its reverse, negate/increment/rotate/word-Toffoli), and a reversible ISA with branch-register control. The single-step transition is verified bijective (step_back o step = identity over all instructions and branch states) and backward execution reconstructs the input; Bennett's construction realizes irreversible functions with clean ancillas. A bijective step erases no bits, hence no Landauer floor. All layers verified exhaustively at small width.

ac103bc