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/tests/test_server.py

@@ -79,7 +79,7 @@ def test_lobby_flow_and_full_game(client):
     assert "needs" in receive_until(host, lambda m: m["type"] == "error")["message"]
 
     host.send_json({"type": "add_ai"})
-    host.send_json({"type": "set_options", "not_equal": True, "hidden_bids": False})
+    host.send_json({"type": "set_options", "hidden_bids": True})
     host.send_json({"type": "start_game"})
 
     rng = random.Random(0)