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.

README.md

@@ -117,11 +117,32 @@ from the strategy budget and returns a legal-direction fallback instead of null
 when its request budget expires. This is best-effort deadline handling, not a
 hard real-time guarantee under CPU saturation.
 
+Version 1.2.0 fixes a search-depth regression from that larger reserve. Prism
+looks one turn deeper in 3-snake rollouts when more than 250 ms remain; with
+Zenith's 50 ms shorter budget that gate was never reached in production, so
+Zenith always stopped at depth 2. Zenith now lowers the gate by its extra
+reserve and deepens after the same elapsed time as Prism.
+
 Run it with:
 ```sh
 SNAKE=ZenithBattleSnake_ClaudeOpus5_5 python main.py
 ```
 
+Show read-only win statistics per own snake version and per opponent from the
+PostgreSQL gameplay database (`GAMEPLAY_DB_PG_DSN`):
+```sh
+just snake-stats --since-hours 24
+just snake-stats --snake-type ZenithBattleSnake --game-type duel --min-games 5
+just snake-stats --since-hours 48 --compare   # opponents side by side per own version
+just snake-stats --traces --since-hours 24    # move-trace latency per version and mode
+```
+
+`--traces` unpacks the newest `--trace-games` (default 300) finished replays and
+reports p50/p90/p99 for strategy time, server overhead (handler minus
+strategy), handler time, network/outside-handler time (engine latency minus
+handler) and engine latency. `ext.timeouts` counts engine timeouts where our
+handler had answered at least 100 ms before the deadline.
+
 Benchmark Apex and Prism against sampled positions from a gameplay database:
 ```sh
 python scripts/benchmark_snakes_from_db.py \