feat: add gameplay stats and restore Zenith rollout depth

- Add read-only gameplay statistics with filters and opponent comparisons.
- Report move-trace latency percentiles and external timeout counts.
- Pair engine latency with the preceding turn to separate timing stages.
- Adjust Zenith rollout deepening for its larger timeout reserve.
- Bump Zenith to 1.2.0 and document the fix and snake-stats command.
- Cover statistics, trace aggregation, rollout depth, and verdict budgets.

tests/scripts/test_move_trace_stats.py

@@ -0,0 +1,61 @@
+import unittest
+
+from scripts.move_trace_stats import add_game, percentile, summary_rows
+from server.database.compact.records import SnakeState, TurnRecord
+
+GAME = {"your_snake_type": "ZenithBattleSnake", "your_snake_version": "1.2.0"}
+
+def _turn(turn: int, thinking: object) -> TurnRecord:
+  return TurnRecord(turn=turn, observed_at=None, move="up", thinking=thinking, food=None, hazards=None)
+
+def _state(snake_id: str, turn: int, latency: int | None) -> SnakeState:
+  return SnakeState(snake_id=snake_id, turn=turn, health=100, latency=latency, body=[])
+
+def _trace(handler: float, strategy: float) -> dict:
+  return {"handler_ms": handler, "strategy_ms": strategy, "budget_ms": 450.0}
+
+class TestMoveTraceStats(unittest.TestCase):
+
+  def test_pairs_engine_latency_of_next_turn(self):
+    groups = {}
+    turns = [
+      _turn(1, {"mode": "duel", "move_trace": _trace(200.0, 195.0)}),
+      _turn(2, {"mode": "duel", "move_trace": _trace(100.0, 90.0)}),
+    ]
+    states = [_state("you", 2, 260), _state("enemy", 2, 499), _state("you", 3, 500)]
+
+    add_game(groups, GAME, "you", turns, states)
+
+    group = groups[("ZenithBattleSnake", "1.2.0", "duel")]
+    self.assertEqual(group.moves, 2)
+    self.assertEqual(group.values["overhead_ms"], [5.0, 10.0])
+    self.assertEqual(group.values["engine_ms"], [260.0, 500.0])
+    self.assertEqual(group.values["network_ms"], [60.0, 400.0])
+    self.assertEqual((group.timeouts, group.timeouts_fast_handler), (1, 1))
+
+  def test_unwraps_raw_thinking_and_labels_missing_mode(self):
+    groups = {}
+    turns = [_turn(1, {"_derived": 0, "_raw": {"move_trace": _trace(5.0, 1.0)}}), _turn(2, "text")]
+
+    add_game(groups, GAME, "you", turns, [_state("you", 2, -32768)])
+
+    group = groups[("ZenithBattleSnake", "1.2.0", "fallback")]
+    self.assertEqual(group.moves, 1)
+    self.assertEqual(group.values["engine_ms"], [])
+
+  def test_summary_formats_percentiles(self):
+    groups = {}
+    add_game(groups, GAME, "you", [_turn(1, {"mode": "multi", "move_trace": _trace(20.0, 18.0)})], [])
+
+    headers, rows = summary_rows(groups)
+
+    self.assertEqual(headers[:4], ["snake", "version", "mode", "moves"])
+    self.assertEqual(rows[0][:6], ["ZenithBattleSnake", "1.2.0", "multi", 1, "0 (0.0%)", 0])
+    self.assertEqual(rows[0][6], "18/18/18")
+    self.assertEqual(rows[0][-1], "-/-/-")
+
+  def test_percentile_of_empty_list(self):
+    self.assertIsNone(percentile([], 0.5))
+
+if __name__ == "__main__":
+  unittest.main()