ResultPort the six-feature linear Q-learner onto the Rust bitboard engine: parity gates and a diagnostic pilot on previously evaluated development seeds

On corrected five-move Hardcore rules the six Klein-Friedmann features are a survival heuristic worth about ten moves and 34,000 points over uniform-random play, an order of magnitude below fair depth-4 in points. Pilot on 256 previously evaluated development seeds (0xa5277000-0xa52770ff, 2,000-move cap, no game censored, 0 illegal decisions): uniform-random legal play 26.25 moves / 73263 points; centre-first 21.01 / 55083; the six features re-learned with the upstream schedule (three exploration seeds) 35.79, 35.81, 36.27 moves and 107147, 107231, 109068 points, a paired gain over random of +9.54 moves [LB95 +8.85] and +33884 points [LB95 +31361] for seed a. The authors' own Python-learned weights (reproduction seed 10) transplanted unchanged live 40.53 moves / 123968 points, +4.74 moves over the engine-learned weights [LB95 +3.77]: same features, same update, same schedule, different opening experience (empty board vs gray row) frozen in by the per-move 1/t step size. Fair d4s7 (drop7-rs, 65,536-entry table) on the first 32 seeds: 380205 points / 110.38 moves, beating the transplanted arm by +256507 points [LB95 +182668] on 31/32 paired games. Slower schedules: per-game 1/g diverged to weights near 1e9 (32.47 moves), harmonic tau 50,000 and the score-reward harmonic arm diverged to NaN (20.90 moves, the rightmost-column policy), constant 0.001 gained +0.50 moves over the upstream schedule [LB95 +0.12], the same size as the +0.48 [+0.07] spread between two identical-configuration seeds. Gates G1-G5 pass; G6 records that a slower stable schedule clears LB95 > 0 by under a move, so theory clause (iv) is not supported at the letter while clauses (iii-a) and (iii-b) are. All CHECK gates (feature parity 54,852 pairs / 0 mismatches; update parity 250 steps / exact; determinism and legality) passed before any diagnostic seed was read. Training ran at about 1.4 million moves per second (1.3 s per 50,000-game arm).