Simplify MCTS scoring to always use root player's perspective

Replaced complex playerId-to-role mapping logic with simpler approach that
always uses the root player's perspective (isDefender_).

The previous implementation tried to determine the requested player's role
from the game state and score from their perspective. However, MCTS scoring
should always be from the root player's perspective - the adversarial logic
(negating scores for opponent moves) happens in the MCTS selection algorithm,
not in the state scoring function.

This simplification:
- Makes the scoring behavior more predictable
- Aligns with MCTS best practices (fixed evaluation perspective)
- Removes unnecessary game state lookups
- Clarifies the separation of concerns between scoring and selection

src/main/cpp/net/eagle0/shardok/ai/mcts/adapters/ShardokGameState.cpp

@@ -42,31 +42,12 @@ uint64_t ShardokGameState::hash() const {
 }
 
 double ShardokGameState::score(MCTSPlayerId playerId) const {
-    // Honor the interface contract: score() should return evaluation from playerId's perspective.
-    // Map the requested playerId to defender/attacker role to determine scoring perspective.
-
-    // Look up which player ID is the defender from game state
-    bool foundDefender = false;
-    bool requestedPlayerIsDefender = false;
-
-    if (state_->player_infos()) {
-        for (const auto* pi : *state_->player_infos()) {
-            if (pi && pi->is_defender()) {
-                foundDefender = true;
-                requestedPlayerIsDefender = (static_cast<PlayerId>(playerId) == pi->player_id());
-                break;
-            }
-        }
-    }
-
-    // Fallback: if we can't determine from game state, use isDefender_ which represents
-    // the root player's role (and playerId is always the root player in practice)
-    const bool scoreFromDefenderPerspective =
-            foundDefender ? requestedPlayerIsDefender : isDefender_;
-
-    // Call score calculator with correct perspective for the requested player
-    return scoreCalculator_
-            ->GuessedStateScore(scoreFromDefenderPerspective, state_, strategy_, castleCoords_);
+    (void)playerId;  // Intentionally unused - we use isDefender_ (fixed at root)
+    // MCTS scoring: Always use root player's perspective (isDefender_) for evaluation.
+    // The playerId parameter represents the root player making decisions in the MCTS tree.
+    // All immediate scores and leaf evaluations must be from this fixed perspective.
+    // Adversarial logic (negation for opponent) happens in MCTS selection, not here.
+    return scoreCalculator_->GuessedStateScore(isDefender_, state_, strategy_, castleCoords_);
 }
 
 MCTSPlayerId ShardokGameState::currentPlayerId() const { return state_->current_player(); }