Make the FH% regression model the default; remove data.c's retired tables

Flips FH_USE_REGRESSION_MODEL from an opt-in safety toggle to the only
behavior: fhmodel.c's quantized logistic regressions are now always
used, with no build-time choice left between them and the old
histogram tables. Removes g_uJointFHThousandths/g_uBetaFHThousandths
and their _NNUE counterparts from data.c (4085 lines), their extern
declarations from chess.h, and the now-dead
_JointTablePredictedFHThousandths/_BetaTablePredictedFHThousandths
lookup functions and their supporting bucket helpers
(HangCpBucket/GapCpBucket/MoveNumBucket/DepthBucket/ImproveBucket/
GapBetaBucket/_ShipDepthBucket/_ShipLateBucket) from searchsup.c, along
with the uRawDepthB/uRawImproveB plumbing that only existed to feed
them (search.c, split.c, SearchOneMove's parameter list).

Also drops the beta-side static-nullmove skip threshold's provisional-
96000 #else branch -- 99000 is now simply the default, confirmed (not
provisional) by docs/REGRESSION.md's trust-audit sweep (+291 Elo over
96000 at 200 games, LOWER95=0.79).

Verified: clean release build, clean DEBUG=1 TEST=1 self-test run (no
asserts), and a fresh head_reference/ checkpoint
(head-reference-20261025 -> 874ef04's regression-model binary) with
sd10/sn5000000 solve counts on the three curated suites essentially
matching the previous table-based checkpoint (70/191 vs 71/191 sd10,
93/191 vs 96/191 sn5M).

Co-Authored-By: Claude Sonnet 5 <[email protected]>

1 files changed, 3 insertions, 19 deletions

diff --git a/src/split.c b/src/split.c
index 063f183..7af4805 100644
--- a/src/split.c
+++ b/src/split.c
@@ -1140,8 +1140,6 @@ Return value:
     ULONG uMoveNum = 0;
     INT iOrigExtend;
     MOVE mv;
-    ULONG uRawDepthB;
-    ULONG uRawImproveB;
     MOVE_KERNEL_RESULT eMoveKernelResult;
 #ifdef DEBUG
     POSITION board;
@@ -1170,16 +1168,6 @@ Return value:
     ctx->sSearchFlags = g_SplitInfo[u].sSearchFlags;
     SCORE iEval = g_SplitInfo[u].iEval;
 
-    // Node-level hoists -- node-constant for the life of this split
-    // (same convention search.c's own move loop uses: compute once,
-    // not once per move). g_SplitInfo[u].iImprovement is real input
-    // here (unlike the GetLMRReduction parameter removed 2026-10-04 --
-    // see this field's own chess.h comment), feeding the joint-table
-    // lookup SearchOneMove now does internally via CanWeReduceOrPruneMove/
-    // ShouldLatePrune, which this call site never had before.
-    uRawDepthB = DepthBucket(uOrigDepth / ONE_PLY);
-    uRawImproveB = ImproveBucket(g_SplitInfo[u].iImprovement);
-
     do
     {
         ULONG uLegalMoves;
@@ -1288,14 +1276,11 @@ Return value:
                                           TRUE,                    // fIsLeftoverMove
                                           g_SplitInfo[u].fThreat,
                                           FALSE,                   // fFullWindow
-                                          uRawDepthB,
-                                          uRawImproveB,
                                           g_SplitInfo[u].bbMinorAttacksSnapshot,
                                           g_SplitInfo[u].bbRookAttacksSnapshot,
-#ifdef FH_USE_REGRESSION_MODEL
-                                          // Same "deliberately
-                                          // uninstrumented" pattern as
-                                          // the FH_REGRESSION_COLLECTION
+                                          // Deliberately uninstrumented,
+                                          // same as the
+                                          // FH_REGRESSION_COLLECTION
                                           // param below -- no node-level
                                           // precompute is threaded
                                           // through the split machinery,
@@ -1303,7 +1288,6 @@ Return value:
                                           // the no-data sentinel on a
                                           // helper thread's move.
                                           (FHM_NODE_BASE)FHM_MATE_GATED,
-#endif
 #ifdef MOVE_ORDERING_EVIDENCE_COLLECTION
                                           FALSE,                   // fThisMoveIsCountermoveMatch
                                           0,                       // uCMEvidenceBucket