feat: add Prism snake and gameplay database lifecycle

- Add bitboard-accelerated Prism and versioned Supreme snake implementations.
- Add database-backed move benchmarks and focused strategy tests.
- Normalize gameplay storage while preserving replay compatibility.
- Add deterministic game quality scoring and replay retention tiers.
- Add backup-first SQLite cleanup, verification, and replacement tooling.
- Add safe compact-plus-delta database merging with conflict detection.
- Extend SQLite and PostgreSQL schemas for replay and quality metadata.
- Add PostgreSQL development service and pytest import configuration.
- Update gameplay documentation and the quart_common submodule revision.

tests/snakes/test_PrismBattleSnake_GPT_5_6_Sol.py

@@ -0,0 +1,68 @@
+import unittest
+
+from snakes import SnakeBuilder, get_snake_version
+from snakes.ApexBattleSnake import ApexBattleSnake
+from snakes.PrismBattleSnake_GPT_5_6_Sol import PrismBattleSnake_GPT_5_6_Sol
+from snakes.bitboard import BitBoard
+
+class TestBitBoard(unittest.TestCase):
+
+  def test_flood_fill_respects_walls(self):
+    board = BitBoard(3, 3)
+    blocked = board.set_to_bits({(1, 0), (1, 1), (1, 2)})
+
+    self.assertEqual(board.flood_count(board.idx(0, 1), blocked), 3)
+    self.assertEqual(board.path_distance(board.idx(0, 1), board.idx(2, 1), blocked), None)
+
+  def test_territory_counts_ties_for_neither_side(self):
+    board = BitBoard(5, 1)
+
+    self.assertEqual(board.territory(board.idx(0, 0), [board.idx(4, 0)], 0), 0)
+
+  def test_nearest_food_returns_shortest_distance(self):
+    board = BitBoard(5, 5)
+    food = board.set_to_bits({(4, 4), (2, 1)})
+
+    self.assertEqual(board.nearest_food(board.idx(0, 0), food, 0), (3, board.idx(2, 1)))
+
+class TestPrismBattleSnake_GPT_5_6_Sol(unittest.TestCase):
+
+  def test_api_name_and_version_are_exposed(self):
+    snake = PrismBattleSnake_GPT_5_6_Sol()
+
+    self.assertEqual(snake.name, "PrismBattleSnake")
+    self.assertEqual(snake.version, "1.0.0")
+    self.assertEqual(get_snake_version("PrismBattleSnake_GPT_5_6_Sol"), "1.0.0")
+    self.assertIsInstance(SnakeBuilder.build("PrismBattleSnake_GPT_5_6_Sol"), PrismBattleSnake_GPT_5_6_Sol)
+
+  def test_bitboard_primitives_match_apex(self):
+    apex = ApexBattleSnake()
+    prism = PrismBattleSnake_GPT_5_6_Sol()
+    blocked = {(1, 0), (1, 1), (3, 2), (3, 3)}
+
+    self.assertEqual(
+      prism._flood_fill_count((0, 0), blocked, 5, 5),
+      apex._flood_fill_count((0, 0), blocked, 5, 5),
+    )
+    self.assertEqual(
+      prism._distance_map((0, 0), blocked, 5, 5),
+      apex._distance_map((0, 0), blocked, 5, 5),
+    )
+    self.assertEqual(
+      prism._path_distance((0, 0), (4, 4), blocked, 5, 5),
+      apex._path_distance((0, 0), (4, 4), blocked, 5, 5),
+    )
+
+  def test_mutated_blocked_set_does_not_return_stale_result(self):
+    snake = PrismBattleSnake_GPT_5_6_Sol()
+    blocked: set[tuple[int, int]] = set()
+
+    open_count = snake._flood_fill_count((1, 1), blocked, 3, 3)
+    blocked.update({(0, 1), (1, 0), (2, 1), (1, 2)})
+    trapped_count = snake._flood_fill_count((1, 1), blocked, 3, 3)
+
+    self.assertEqual(open_count, 9)
+    self.assertEqual(trapped_count, 1)
+
+if __name__ == "__main__":
+  unittest.main()