feat: add Zenith strategy and move latency tracing

- Register Zenith 1.1 with balanced duel verdicts and forced-outcome overrides.
- Prioritize permanent-trail space in Constrictor and health-aware hazard routes.
- Deduct executor queue delays and return fallback directions on move timeouts.
- Correlate response headers, replay timings, and sampled structured trace logs.
- Move shared metrics publication off the response path without losing local counts.
- Allow configurable tournament opponents and add a psql helper recipe.
- Preserve empty latency values through compact replay encoding and migration.
- Update Arena game links and use default assets for missing customizations.
- Cover strategy, HTTP lifecycle, tracing, replay codecs, and dashboard behavior.
- Validate with 260 passing Python tests, 4 skips, and 2 passing JavaScript tests.

snakes/engine/survival_search.py

@@ -235,7 +235,7 @@ class CompactSurvivalSearch:
     blocked = self._occupied(mine, enemies) & ~(1 << mine[0])
     space = self.board.flood_count(mine[0], blocked)
     liberties = self.board.open_neighbor_count(mine[0], blocked)
-    if liberties == 0 or space < len(mine):
+    if liberties == 0 or (not self.is_constrictor and space < len(mine)):
       return self.DEATH
     enemy_pressure = 0.0
     for enemy in enemies: