games: the clock beats the walk button, and the rack isn't betting

The trivia ladder handled a walk before it looked at the clock, so the
timeout only ever bit if the browser volunteered it. Sit on a question,
look it up, answer if you find it and walk if you don't, and you never
lose a ladder. The clock is now the first thing that happens to a move.

The house's chip rack was wired up as bet buttons on blackjack and
hangman: it's four spans with data-chip on them and nothing said the
handler only wanted the real ones. Clicking the house's money raised
your bet.

Hangman had two definitions of "a letter you'd guess" — unicode in the
engine, ASCII in the renderer — and a phrase with an accent in it would
have had no tile to fill and no key to fill it with. One definition now.

Plus: trivia's countdown no longer freezes at zero when the server turns
down a timeout report it was early for, questions whose wrong answer
decodes into the right one are dropped at the door, and hangman bets on
PeteFX's spot like every other table instead of its own copy of it.

internal/opentdb/opentdb.go

@@ -146,8 +146,22 @@ func (c *Client) Fetch(ctx context.Context, difficulty string, n int) ([]trivia.
 		// the right answer sits in the bank never reaches a player.
 		answers := make([]string, 0, 4)
 		answers = append(answers, correct)
+		dupe := false
 		for _, w := range r.Incorrect {
-			answers = append(answers, clean(w))
+			a := clean(w)
+			// A wrong answer that reads the same as the right one — usually two
+			// spellings that collapse once the entities are decoded — is a question
+			// with two identical buttons on it, and the shuffle can only call one of
+			// them correct. A player who clicked the right words and was told they
+			// were wrong has lost the whole ladder to our typography. Drop it.
+			if a == "" || a == correct {
+				dupe = true
+				break
+			}
+			answers = append(answers, a)
+		}
+		if dupe || len(answers) != 4 {
+			continue
 		}
 		qs = append(qs, trivia.Question{
 			Category: clean(r.Category),