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/app/service.py

@@ -126,9 +126,9 @@ class WizardService:
                     seat.session.send(protocol.error("You were removed from the lobby"))
                     self._send_no_lobby(seat.session)
                 lobby.broadcast()
-            case protocol.SetOptions(not_equal=not_equal, hidden_bids=hidden_bids):
+            case protocol.SetOptions(hidden_bids=hidden_bids):
                 lobby = self._lobby_of(session)
-                lobby.set_options(session, GameOptions(not_equal=not_equal, hidden_bids=hidden_bids))
+                lobby.set_options(session, GameOptions(hidden_bids=hidden_bids))
                 lobby.broadcast()
             case protocol.StartGame():
                 lobby = self._lobby_of(session)