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.

scripts/migrate_gameplay_database.py

@@ -143,6 +143,12 @@ def copy_game_snakes(source:sqlite3.Connection, destination:sqlite3.Connection,
   has_game_snakes = source.execute("""
     SELECT 1 FROM sqlite_master WHERE type = 'table' AND name = 'game_snakes'
   """).fetchone() is not None
+  sql = """
+    INSERT OR IGNORE INTO game_snakes (
+      game_id, snake_id, snake_name, is_you, customizations_json
+    ) VALUES (?, ?, ?, ?, ?)
+  """
+  count = 0
   if has_game_snakes:
     columns = object_columns(source, "game_snakes")
     customizations = (
@@ -153,24 +159,26 @@ def copy_game_snakes(source:sqlite3.Connection, destination:sqlite3.Connection,
       SELECT game_id, snake_id, snake_name, is_you, {customizations}
       FROM game_snakes ORDER BY game_id, snake_id
     """)
-  else:
-    cursor = source.execute("""
-      SELECT game_id, snake_id, MAX(snake_name), MAX(is_you),
-        '{}' AS customizations_json
-      FROM snake_turns
-      GROUP BY game_id, snake_id
-      ORDER BY game_id, snake_id
-    """)
-  sql = """
-    INSERT INTO game_snakes (
-      game_id, snake_id, snake_name, is_you, customizations_json
-    ) VALUES (?, ?, ?, ?, ?)
-  """
-  count = 0
+    while rows := cursor.fetchmany(batch_size):
+      retained_rows = [tuple(row) for row in rows if row[0] in retained_ids]
+      before = destination.total_changes
+      destination.executemany(sql, retained_rows)
+      count += destination.total_changes - before
+
+  # Older databases can contain an empty or only partially populated
+  # game_snakes table. Always synthesize missing identities from snake_turns.
+  cursor = source.execute("""
+    SELECT game_id, snake_id, MAX(snake_name), MAX(is_you),
+      '{}' AS customizations_json
+    FROM snake_turns
+    GROUP BY game_id, snake_id
+    ORDER BY game_id, snake_id
+  """)
   while rows := cursor.fetchmany(batch_size):
     retained_rows = [tuple(row) for row in rows if row[0] in retained_ids]
+    before = destination.total_changes
     destination.executemany(sql, retained_rows)
-    count += len(retained_rows)
+    count += destination.total_changes - before
   return count
 
 def decode_json(value:str|None, fallback):