fix: resolve duel roots and recover legacy snake data

- Resolve selected moves and enemy replies on the same simulated turn.
- Add an Apex candidate hook and bump the Prism snake to version 1.1.0.
- Rebuild benchmark states from normalized turn data when snapshots are empty.
- Synthesize missing game snake identities during legacy database migration.
- Add regression coverage for duel timing and partial legacy schemas.

tests/snakes/test_PrismBattleSnake_GPT_5_6_Sol.py

@@ -51,8 +51,8 @@ class TestPrismBattleSnake_GPT_5_6_Sol(unittest.TestCase):
     snake = PrismBattleSnake_GPT_5_6_Sol()
 
     self.assertEqual(snake.name, "PrismBattleSnake")
-    self.assertEqual(snake.version, "1.0.1")
-    self.assertEqual(get_snake_version("PrismBattleSnake_GPT_5_6_Sol"), "1.0.1")
+    self.assertEqual(snake.version, "1.1.0")
+    self.assertEqual(get_snake_version("PrismBattleSnake_GPT_5_6_Sol"), "1.1.0")
     self.assertIsInstance(SnakeBuilder.build("PrismBattleSnake_GPT_5_6_Sol"), PrismBattleSnake_GPT_5_6_Sol)
 
   def test_bitboard_primitives_match_apex(self):
@@ -100,6 +100,50 @@ class TestPrismBattleSnake_GPT_5_6_Sol(unittest.TestCase):
 
     self.assertGreater(value, 0)
 
+  def test_candidate_search_resolves_enemy_reply_on_the_same_turn(self):
+    board = BitBoard(3, 3)
+    search = BitboardDuelSearch(
+      board=board, food=set(), hazards=set(), hazard_count={},
+      hazard_damage=15, deadline=None,
+    )
+    my_body = [{"x": 0, "y": 1}, {"x": 0, "y": 0}]
+    enemy_body = [{"x": 2, "y": 1}, {"x": 2, "y": 0}]
+
+    value, depth = search.search_candidate(
+      my_body=my_body,
+      enemy_body=enemy_body,
+      my_target=(1, 1),
+      my_health=100,
+      enemy_health=100,
+      max_depth=1,
+      previous_hazards=set(),
+    )
+
+    self.assertEqual(value, -500.0)
+    self.assertEqual(depth, 1)
+
+  def test_candidate_search_does_not_advance_our_snake_twice_at_root(self):
+    board = BitBoard(4, 1)
+    search = BitboardDuelSearch(
+      board=board, food=set(), hazards=set(), hazard_count={},
+      hazard_damage=15, deadline=None,
+    )
+    my_body = [{"x": 0, "y": 0}]
+    enemy_body = [{"x": 3, "y": 0}]
+
+    value, depth = search.search_candidate(
+      my_body=my_body,
+      enemy_body=enemy_body,
+      my_target=(1, 0),
+      my_health=100,
+      enemy_health=100,
+      max_depth=1,
+      previous_hazards=set(),
+    )
+
+    self.assertEqual(value, 0.0)
+    self.assertEqual(depth, 1)
+
   def test_duel_search_keeps_tail_blocked_when_its_snake_eats(self):
     board = BitBoard(3, 3)
     search = BitboardDuelSearch(

tests/test_MigrateGameplayDatabase.py

@@ -47,6 +47,54 @@ class TestMigrateGameplayDatabase(unittest.TestCase):
         '{"color":"#663399","head":"ferret","tail":"swirl"}',
       ))
 
+  def test_copy_game_snakes_synthesizes_rows_when_table_is_empty(self):
+    source = sqlite3.connect(":memory:")
+    destination = sqlite3.connect(":memory:")
+    try:
+      source.execute("""
+        CREATE TABLE game_snakes (
+          game_id TEXT, snake_id TEXT, snake_name TEXT, is_you INTEGER,
+          customizations_json TEXT NOT NULL DEFAULT '{}'
+        )
+      """)
+      source.execute("""
+        CREATE TABLE snake_turns (
+          game_id TEXT, snake_id TEXT, snake_name TEXT, is_you INTEGER
+        )
+      """)
+      source.executemany(
+        "INSERT INTO snake_turns VALUES (?, ?, ?, ?)",
+        [
+          ("game-1", "snake-1", "PrismBattleSnake", 1),
+          ("game-1", "snake-1", "PrismBattleSnake", 1),
+          ("game-1", "snake-2", "Enemy", 0),
+        ],
+      )
+      destination.execute("""
+        CREATE TABLE game_snakes (
+          game_id TEXT, snake_id TEXT, snake_name TEXT, is_you INTEGER,
+          customizations_json TEXT NOT NULL DEFAULT '{}',
+          PRIMARY KEY (game_id, snake_id)
+        )
+      """)
+
+      copied = copy_game_snakes(
+        source, destination, batch_size=10, retained_ids={"game-1"},
+      )
+      rows = destination.execute("""
+        SELECT snake_id, snake_name, is_you, customizations_json
+        FROM game_snakes ORDER BY snake_id
+      """).fetchall()
+    finally:
+      source.close()
+      destination.close()
+
+    self.assertEqual(copied, 2)
+    self.assertEqual(rows, [
+      ("snake-1", "PrismBattleSnake", 1, "{}"),
+      ("snake-2", "Enemy", 0, "{}"),
+    ])
+
   def test_copy_game_snakes_defaults_legacy_schema_to_empty_customizations(self):
     source = sqlite3.connect(":memory:")
     destination = sqlite3.connect(":memory:")
@@ -60,6 +108,11 @@ class TestMigrateGameplayDatabase(unittest.TestCase):
         "INSERT INTO game_snakes VALUES (?, ?, ?, ?)",
         ("game-1", "snake-1", "LegacySnake", 0),
       )
+      source.execute("""
+        CREATE TABLE snake_turns (
+          game_id TEXT, snake_id TEXT, snake_name TEXT, is_you INTEGER
+        )
+      """)
       destination.execute("""
         CREATE TABLE game_snakes (
           game_id TEXT, snake_id TEXT, snake_name TEXT, is_you INTEGER,