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/README.md

@@ -11,7 +11,7 @@ pip install ./wizard_server/game_logic
 import random
 from wizard_game import WizardGame, GameOptions
 
-game = WizardGame(num_players=4, options=GameOptions(not_equal=True), seed=1)
+game = WizardGame(num_players=4, options=GameOptions(hidden_bids=True), seed=1)
 rng = random.Random(1)
 while not game.is_finished:
     player = game.current_player