Second continuation of the depth-5-distilled NNUE leaf evolution: resume from the plateau population with a slower mutation-size decay (up to 1,000 further generations)

Valid run of the frozen protocol EX-20260903-nnue-evolution-continuation2-d3-80eebad3 (second successor to the theory, third experiment in the series), every stage completed, every artifact with zero illegal and zero incomplete decisions. Stage C resumed from the second experiment's checkpointed generation-150 population (SHA-256 33dcc25b88ab56a0a80329bf11983b539883aa922900b03de3cea71e1da3529d) with that experiment's frozen candidate (SHA-256 759084fab97599818d01a5da6d18b9cc77172249f09a68d5104361bca385e09b) as the third paired control, testing whether a 3.75x slower mutation-size decay (time constant 1,500 generations vs. 400 before; sigma stayed at 0.0500 at generation 0, 0.0453 at the stop, versus 0.0345 at the equivalent generation last time) would let evolution get further past the point where the prior run plateaued. The identical preregistered plateau rule stopped this run at the identical generation as before, 149: the check after generation 99 found the paired margin over the fair control rising at +201.7 points per generation (lower bound +11.7, versus +239 and +30 in the second experiment) and continued; the check after generation 149 found +164.0 per generation (lower bound -28.5, versus +37 and -159 before) and stopped. The improvement rate at the stopping point was more than four times the prior run's (164 against 37 points/generation), and the best candidate beat the fair control on 26 of 150 blocks against 9 in the second experiment, but the lower bound of the fitted slope still crossed zero at the same 100-generation checkpoint, so the rule fired regardless. Fifty-generation population-mean averages: 235,353, 238,797, 244,800 (rising monotonically, unlike the second experiment's flat third block); paired margin over the immediately-prior candidate +4,301, -949, +13,589; over the fair control -99,479, -88,006, -77,654. Training-signal falsifier fails again (population mean above fair in 0 of the last 10 generations, margin -70,199; best above fair in 4 of the last 10). Elite re-selection on 128 fresh games (0xa52eb3c0) froze candidate-28 at 257,314 (finalists 232,499 to 257,314, a tighter spread than the second experiment's). Stage D, 64 never-read games (0xa52f2100, opened once at 2026-09-04T08:56:37Z after the candidate's SHA-256 was recorded), five arms: this candidate averaged 249,757 against the frozen fair leaf's 335,266, paired -85,509 (bootstrap 95% bounds -128,482 to -43,591, Student-t lower bound -129,423, floor 43,272), W-T-L 22-0-42, both halves negative (-59,644 / -111,374), lower quartile 156,534 against 176,108: every screen criterion fails, scientific outcome fail for this configuration, consistent with both prior screens. The preregistered secondary contrast is the key negative finding of this run: the candidate beat the immediately-prior (second experiment's) frozen candidate by only +13,572 on the same seeds, with a bootstrap 95% lower bound of -30,165 and a Student-t lower bound of -30,869 -- both crossing zero (detection floor 43,791), W-T-L 31-0-33. Unlike the second experiment's clearly positive +36,278 (lower bound +9,085) over the first experiment's candidate, this third experiment's gain over the second is NOT statistically distinguishable from zero at this screen size: three months of relatively larger mutations bought a point estimate about a third the size of the previous continuation's out-of-sample gain, and it is not confidently positive. The second experiment's candidate itself scored -99,081 against the fair leaf on this fresh block (lower bound -154,094), broadly consistent with its own screen result of -68,441 (lower bound -112,090), a second informal replication. Over the warm start the candidate is +106,846 (lower bound +76,970). The reference arm gave fair depth 4 minus fair depth 3 of -1,409 (bounds -62,290 to +58,933, crossing zero on this cohort, a diagnostic-only reading and not comparable across screens with different fresh seeds). Read together with the second experiment: slowing the mutation-size decay produced a visibly healthier training curve (a still-rising population mean through all three 50-generation blocks, more generations where the best candidate beat the fair control) but did NOT produce a statistically confirmed improvement over the immediately-prior candidate on held-out games, and the plateau rule still stopped the run at the same generation. The most defensible reading is that the annealing schedule was not the dominant cause of the earlier plateau -- something else (population size, games per candidate, or the leaf class's genuine ceiling under this search depth) is the binding constraint, though a schedule 3.75x slower is not proof that no schedule would help; a much slower schedule, or removing the anneal-driven exploration decay entirely in favour of a fixed sigma with more games per candidate, remains untested.