Add UNO sudden death and multiplayer bot turn announcements

2-player UNO (especially No Mercy) regularly stalls past 100 turns.
Sudden death announces at turn 80 with a 20-turn countdown, then
scores hands by card point values — lowest total wins. Applies to
solo (vs bot) and multiplayer when 2 active players remain.

Also adds "It's X's turn" labels to bot plays in multiplayer,
matching the format human plays already had, and adds sudden death
checks to all turn advancement paths.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/plugin/uno_test.go

@@ -288,3 +288,58 @@ func TestUnoColor_Emoji(t *testing.T) {
 		t.Errorf("blue emoji: got %q", unoBlue.Emoji())
 	}
 }
+
+// ---------------------------------------------------------------------------
+// Card point values (sudden death scoring)
+// ---------------------------------------------------------------------------
+
+func TestCardPointValue(t *testing.T) {
+	tests := []struct {
+		name string
+		card unoCard
+		want int
+	}{
+		{"zero", unoCard{unoRed, unoZero}, 0},
+		{"five", unoCard{unoBlue, unoFive}, 5},
+		{"nine", unoCard{unoGreen, unoNine}, 9},
+		{"skip", unoCard{unoRed, unoSkip}, 20},
+		{"reverse", unoCard{unoBlue, unoReverse}, 20},
+		{"draw two", unoCard{unoYellow, unoDrawTwo}, 20},
+		{"skip everyone", unoCard{unoRed, unoSkipEveryone}, 30},
+		{"draw four colored", unoCard{unoGreen, unoDrawFour}, 30},
+		{"discard all", unoCard{unoBlue, unoDiscardAll}, 30},
+		{"wild", unoCard{unoWild, unoWildCard}, 50},
+		{"wild draw four", unoCard{unoWild, unoWildDrawFour}, 50},
+		{"wild reverse draw 4", unoCard{unoWild, unoWildReverseDraw4}, 60},
+		{"wild draw six", unoCard{unoWild, unoWildDrawSix}, 60},
+		{"wild color roulette", unoCard{unoWild, unoWildColorRoulette}, 60},
+		{"wild draw ten", unoCard{unoWild, unoWildDrawTen}, 75},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := cardPointValue(tt.card); got != tt.want {
+				t.Errorf("cardPointValue(%v) = %d, want %d", tt.card, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestScoreHand(t *testing.T) {
+	hand := []unoCard{
+		{unoRed, unoFive},       // 5
+		{unoBlue, unoNine},      // 9
+		{unoGreen, unoSkip},     // 20
+		{unoWild, unoWildCard},  // 50
+	}
+	got := scoreHand(hand)
+	want := 84
+	if got != want {
+		t.Errorf("scoreHand() = %d, want %d", got, want)
+	}
+}
+
+func TestScoreHandEmpty(t *testing.T) {
+	if got := scoreHand(nil); got != 0 {
+		t.Errorf("scoreHand(nil) = %d, want 0", got)
+	}
+}