nx_boolsynth4.nx

nx_boolsynth4.nx -- L8 gate-level synthesis, 4-input (extends the team's proven 3-input superopt up the hardware rung). The team AUTHORS a minimal straight-line circuit for any 4-input boolean function by SEARCH, and the result is verified EXACTLY and FREE by the truth-table-as-bitmask trick: drive the four inputs with the columns 0xAAAA / 0xCCCC / 0xF0F0 / 0xFF00, and the 16-bit output word IS the function's truth table -- so circuit==target is one integer compare, all 16 rows at once, no execution. Gate count is a DETERMINISTIC counted invariant (nx_cost_oracle), so the win vs a naive sum-of-products baseline is judged objectively, not by wall-clock or self-assessment. Honest scope: the search is the chain class (each gate combines the running value with a PRIMARY input) -- a real straight-line subclass that captures reduce/parity/threshold forms; the full DAG search + real gcc/clang race (the existing 71-win 3-input standing) is the triangulation rung above this. license_tier: ORIGINAL