router/semantic: slice 20 pretrained fine-tune report — in-pool best, LOFO 1.000

cointegrated/rubert-tiny fine-tuned end-to-end: pair ordering 0.933-0.970
(+0.56-0.78 margin, in-pool) beats every from-scratch config, but the
held-out capability-question family fires 126/126 as action on all 18
config/seeds (FA_rate 1.000, mean proba 0.86-0.99, family σ 0.0045). tiny2
ceiling (newer, larger vocab) does not move LOFO (1.000) and is worse
in-pool. sparse 0.667 remains the safety floor; supervised encoder scaling
ruled out for the generator boundary.

docs/evals/CLAUDE.md

@@ -52,6 +52,7 @@ A pair in `docs/routing.md` went stale unnoticed. Its source predated the
 | [Slice 17 nonlinear e5 MLP probe](2026-09-07-nonlinear-e5-mlp-probe.md) | live |
 | [Sparse lexical action-gate probe (slice 18)](2026-09-07-sparse-lexical-action-gate.md) | live |
 | [From-scratch tiny sequence pragmatics specialist (slice 19)](2026-09-08-tiny-sequence-pragmatics-specialist.md) | live |
+| [Pretrained rubert-tiny pragmatics baseline (slice 20)](2026-09-07-pretrained-rubert-tiny-pragmatics-baseline.md) | live |
 
 `docs/routing.md` holds the arm table these feed. Cite from there, not from here.