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, 7 insertions, 40 deletions

diff --git a/src/testsup.c b/src/testsup.c
index c5c62c2..379cbab 100644
--- a/src/testsup.c
+++ b/src/testsup.c
@@ -22,46 +22,13 @@ Revision History:
 
 #include "chess.h"
 
-FLAG
-IsBoardLegal(POSITION *pos)
-{
-    COOR c;
-    
-    for (c = A1; c <= H1; c++)
-    {
-        if (!IS_EMPTY(pos->rgSquare[c].pPiece))
-        {
-            if (IS_PAWN(pos->rgSquare[c].pPiece))
-            {
-                return(FALSE);
-            }
-        }
-    }
-    
-    for (c = A8; c <= H8; c++)
-    {
-        if (!IS_EMPTY(pos->rgSquare[c].pPiece))
-        {
-            if (IS_PAWN(pos->rgSquare[c].pPiece))
-            {
-                return(FALSE);
-            }
-        }
-    }
-    
-    if (InCheck(pos, WHITE) &&
-        InCheck(pos, BLACK))
-    {
-        return(FALSE);
-    }
-
-    if (InCheck(pos, FLIP(pos->uToMove)))
-    {
-        return(FALSE);
-    }
-    return(TRUE);
-}
-
+// IsBoardLegal moved to board.c (2026-10-15) -- it's not test-only:
+// gamelist.c's SetRootPosition needs it on every build profile to
+// reject an illegal FEN (e.g. the side not on move left in check)
+// before it ever reaches search, not just under TEST/EVAL_DUMP, which
+// is all that linked this file in before. Declaration unchanged
+// (chess.h), callers unchanged (including TestLegalMoveGenerator,
+// below).
 
 void
 GenerateRandomLegalPosition(POSITION *pos)