Fix several latent search/move-generation bugs found via NNUE annotation tooling

- probe.c: EGTB win/loss scores now render as +-MATE100 (literal +-NMATE)
  instead of a misleading float, matching how a real forced mate prints.
- hash.c: fix a sign error in StoreExactScore's loss-side hash bound
  (iValue +NMATE paired with HASH_FLAG_UPPER, should be -NMATE) -- dormant
  until the probe.c fix made it reachable every EGTB loss.
- san.c: a checking castle move (O-O+/O-O-O+) printed as +-O/+-O-O --
  the check-suffix pointer was captured before strcpy filled the
  buffer, so '+' overwrote the leading 'O' instead of appending.
- search.c/searchsup.c: MATEMOVE/DRAWMOVE/RECOGNMOVE/EGTBMOVE now record
  into the PV unconditionally instead of only when the ambient alpha-beta
  window happens to strictly contain the score -- these are exact,
  game-theoretic results, not heuristic bounds, so a PVS scout-window
  tie (common once a line's value is already known) shouldn't suppress
  them. This is why <#>/<=>/<REC>/<EGTB> almost never showed up in a
  printed PV.
- util.c: WalkPV now reconstructs a still-missing final move/sentinel
  directly from the board when the recorded PV runs out one ply short
  of (or exactly at) a forced mate/stalemate/draw, instead of leaving
  the printed PV silently truncated.
- gamelist.c/board.c/testsup.c: SetRootPosition now parses into a local
  staging POSITION and validates IsBoardLegal + VerifyPositionConsistency
  (both moved/enabled for all build profiles, not just TEST/EVAL_DUMP)
  before committing to g_RootPosition. Previously a rejected setboard
  (e.g. a hand-built FEN leaving the side not on move in check) still
  left the partially-parsed, illegal position in g_RootPosition for the
  next `go` to search -- GetRootPosition() hands out a stable pointer
  straight to it with no defensive copy -- causing a crash instead of
  the clean "Error (malformed FEN)" rejection already printed.

All verified via precommit_check.sh (TEST=1 self-test suite + DEBUG
smoke test) in addition to targeted manual repros for each bug.

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

1 files changed, 32 insertions, 26 deletions

diff --git a/src/search.c b/src/search.c
index 9350fad..8404d9d 100644
--- a/src/search.c
+++ b/src/search.c
@@ -544,17 +544,20 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
         case UNRECOGNIZED:
             break;
         case RECOGN_EXACT:
-            if ((iAlpha < iScore) && (iScore < iBeta))
-            {
-                UpdatePV(ctx, RECOGNMOVE);
-            }
+            // Unconditional: a recognizer-proven exact result is a
+            // game-theoretic fact about this position, not a bound --
+            // unlike an ordinary heuristic score, it can't be "wrong"
+            // for having been reached outside the ambient (alpha,
+            // beta) window, so it deserves to be recorded regardless
+            // (see CLAUDE.md's MATEMOVE/DRAWMOVE/RECOGNMOVE/EGTBMOVE
+            // writeup -- all five sentinel cases shared this same
+            // gate, which is why <REC>/<EGTB>/<#>/<=> almost never
+            // showed up in a printed PV).
+            UpdatePV(ctx, RECOGNMOVE);
             iBestScore = iScore;
             goto end;
         case RECOGN_EGTB:
-            if ((iAlpha < iScore) && (iScore < iBeta))
-            {
-                UpdatePV(ctx, EGTBMOVE);
-            }
+            UpdatePV(ctx, EGTBMOVE);
             iBestScore = iScore;
             goto end;
         case RECOGN_LOWER:
@@ -1203,22 +1206,22 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx,
             ASSERT(IS_CHECKING_MOVE(mvLast));
             ASSERT(InCheck(pos, pos->uToMove));
             iBestScore = MATED_SCORE(ctx->uPly);
-            if ((iAlpha < iBestScore) && (iBestScore < iBeta))
-            {
-                INC(ctx->sCounters.tree.u64LeafCount);
-                UpdatePV(ctx, MATEMOVE);
-            }
+            // Unconditional -- see the RecognLookup sites above: a
+            // checkmate is an exact, game-theoretic fact about this
+            // position, not a bound, so it can't be "wrong" for
+            // having been reached outside the ambient window.
+            INC(ctx->sCounters.tree.u64LeafCount);
+            UpdatePV(ctx, MATEMOVE);
             ASSERT(iBestScore <= -NMATE);
             goto end;
         }
         else
         {
             iBestScore = g_iDrawScore[pos->uToMove];
-            if ((iAlpha < iBestScore) && (iBestScore < iBeta))
-            {
-                INC(ctx->sCounters.tree.u64LeafCount);
-                UpdatePV(ctx, DRAWMOVE);
-            }
+            // Unconditional -- same reasoning as the MATEMOVE case
+            // just above: stalemate is exact, not a bound.
+            INC(ctx->sCounters.tree.u64LeafCount);
+            UpdatePV(ctx, DRAWMOVE);
             goto end;
         }
     }
@@ -2167,17 +2170,20 @@ QSearch(IN SEARCHER_THREAD_CONTEXT *ctx,
         case UNRECOGNIZED:
             break;
         case RECOGN_EXACT:
-            if ((iAlpha < iScore) && (iScore < iBeta))
-            {
-                UpdatePV(ctx, RECOGNMOVE);
-            }
+            // Unconditional: a recognizer-proven exact result is a
+            // game-theoretic fact about this position, not a bound --
+            // unlike an ordinary heuristic score, it can't be "wrong"
+            // for having been reached outside the ambient (alpha,
+            // beta) window, so it deserves to be recorded regardless
+            // (see CLAUDE.md's MATEMOVE/DRAWMOVE/RECOGNMOVE/EGTBMOVE
+            // writeup -- all five sentinel cases shared this same
+            // gate, which is why <REC>/<EGTB>/<#>/<=> almost never
+            // showed up in a printed PV).
+            UpdatePV(ctx, RECOGNMOVE);
             iBestScore = iScore;
             goto end;
         case RECOGN_EGTB:
-            if ((iAlpha < iScore) && (iScore < iBeta))
-            {
-                UpdatePV(ctx, EGTBMOVE);
-            }
+            UpdatePV(ctx, EGTBMOVE);
             iBestScore = iScore;
             goto end;
         case RECOGN_LOWER: