random: port Alea, one generator per character

pqcli used Python's global Mersenne Twister, seeded once from the clock.
Upstream uses Johannes Baagøe's Alea, with Random(n) = uint32() % n, and
keeps the generator state with each character. The port matches the JS
output bit for bit, including UTF-16 seeding of non-BMP characters.

Each Player now owns an Alea that is pickled with the save, and
Simulation.tick draws from it. Saves without one get a fresh generator.
As upstream does, a new character's game continues from the state the
kept stat roll was made from.

The parity traces are re-recorded, since every random number changes.

pqcli/ui/basic/__init__.py

@@ -124,7 +124,11 @@ class BasicUserInterface(BaseUserInterface):
                 break
 
         player = create_player(
-            name=name, race=race, class_=class_, stats=stats
+            name=name,
+            race=race,
+            class_=class_,
+            stats=stats,
+            seed=stats_builder.seed,
         )
         self.roster.players.append(player)
         if auto_play and self.confirm(