Remove dead EFP references left over from its removal

EFP (extended futility pruning) was removed from Search()'s move loop
in favor of LMP's joint FH% table, but several comments, a dead
counter (u64EFPPruned, never incremented anywhere), and two unused
defines (EFP_FH_MIN_SAMPLES/EFP_FH_PRUNE_THRESHOLD_PCT_THOUSANDTHS)
were left behind claiming EFP still gates something. Clean these up:

- Delete u64EFPPruned (COUNTERS and g_Options) and its dead
  reader/writer in root.c.
- Delete the two unused EFP_FH_* defines in search.c, and the stale
  fAnyMoveEFPPruned comment describing a branch that no longer
  skips a store.
- Fix dangling prose references to EFP in generate.c, chess.h,
  searchsup.c, and testsearch.c that describe present-tense behavior
  EFP no longer participates in, preserving the historical rationale
  where it's still relevant (e.g. why EstimateHangingMaterialCp can
  return a negative value).

Deliberately left alone (flagged for a separate decision, not a
clear delete): script.c's still-live JOINT_EXTRA_VERIFY calibration
labels ("EFP tier1/tier2"), search.c's _PostReduceDepthBucketEfpAligned
(same live mechanism, name only), searchsup.c's LMP_BASE_MOVENUM/
LMP_PER_PLY_MOVENUM dead macros (kept pending a real floor/ceiling
decision), and PLY_INFO.iPositional[2] (now write-only, but removing
it touches Eval()'s call signature everywhere).

Comment/dead-code only, no logic touched.

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

1 files changed, 6 insertions, 9 deletions

diff --git a/src/chess.h b/src/chess.h
index 94c9db4..36b90e3 100755
--- a/src/chess.h
+++ b/src/chess.h
@@ -1268,10 +1268,6 @@ typedef struct _COUNTERS
         // leftover pool near the leaves. Counts every move this was
         // applied to.
         UINT64 u64LMPPruned;
-        // 2026-10-05: extended futility pruning (EFP, search.c) -- same
-        // shape as u64LMPPruned above, for the other overt-skip (not
-        // reduction) mechanism in the move loop.
-        UINT64 u64EFPPruned;
         // 2026-10-05: null-move R-factor breakdown -- which whole-ply R
         // SelectNullmoveRFactor chose, and how often the null-move
         // search at that R actually failed high. Indexed by R/ONE_PLY,
@@ -1709,9 +1705,11 @@ typedef struct _PLY_INFO
     // -- e.g. a cleaner cross-ply "improving" signal that corrects for
     // a tier switch (super-lazy vs full) between the two Eval() calls
     // being compared, instead of just diffing raw iEval values. Not
-    // yet consumed that way anywhere; currently only the search.c EFP
-    // gate (VALUE_KNIGHT/VALUE_ROOK margins) reads this, for the
-    // node-it-was-computed-at only.
+    // yet consumed that way anywhere; its one reader (search.c's EFP
+    // gate, VALUE_KNIGHT/VALUE_ROOK margins) was removed along with
+    // EFP, so this is currently write-only -- flagged, not deleted,
+    // since removing it means touching Eval()'s piPositional parameter
+    // at every call site, a bigger change than this cleanup pass.
     SCORE iPositional[2];
     INT iExtensionAmount;
     FLAG fInCheck;
@@ -2077,7 +2075,6 @@ typedef struct _GAME_OPTIONS
     UINT64 u64JointExtraTries[JOINT_EXTRA_TIER_COUNT];
     UINT64 u64JointExtraResearch[JOINT_EXTRA_TIER_COUNT];
     UINT64 u64LMPPruned;
-    UINT64 u64EFPPruned;
     UINT64 u64NullMoveTriesByR[NULL_R_BUCKETS];
     UINT64 u64NullMoveSuccessByR[NULL_R_BUCKETS];
 #ifdef PRUNE_VERIFY
@@ -2953,7 +2950,7 @@ TestMakeUnmakeMove(void);
 // Countermove-match tier bonus, placed above GOOD_MOVE (see
 // generate.c's _ScoreAllMoves quiet-move branch) so a *sufficiently
 // evidenced* match (see COUNTERMOVE_EVIDENCE_THRESHOLD) escapes
-// "leftover" classification -- and the fIsLeftoverMove-gated EFP check --
+// "leftover" classification -- and the fIsLeftoverMove-gated LMP check --
 // entirely, becoming its own tier alongside killers. Conservatively
 // placed below both ply-2 killer slots (FOURTH_KILLER/THIRD_KILLER):
 // the contested-node A/B harness never found clean evidence a