Always forbid bids that add up to the cards in hand

The sum of all bids may never equal the number of cards each player
holds in the round; the last bidder has to adjust their bid. This was an
optional "not equal" lobby setting and is now a fixed rule of the game
engine, so it applies to humans, AI players and training alike.

- Remove GameOptions.not_equal, the set_options field, the lobby toggle
  and the --not-equal training flag
- Explain the rule in the lobby and show the blocked bid while bidding
- Drop the option from the AI observation encoding
- Tests check that no round ends with bids summing to the cards in hand

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

wizard_server/game_logic/wizard_game/game.py

@@ -217,11 +217,14 @@ class WizardGame:
         return rnd
 
     def _allowed_bids(self, player: int) -> list[int]:
+        """Bids 0..cards in hand, except that the last bidder may not make the
+        sum of all bids equal the number of cards each player holds this round.
+        """
         rnd = self.round
         allowed = list(range(rnd.round_number + 1))
         placed = [bid for bid in rnd.bids if bid is not None]
         is_last_bidder = len(placed) == self.num_players - 1 and rnd.bids[player] is None
-        if self.options.not_equal and is_last_bidder:
+        if is_last_bidder:
             forbidden = rnd.round_number - sum(placed)
             allowed = [bid for bid in allowed if bid != forbidden]
         return allowed