Keep held dice held between throws

Picking the same three dice again after every throw is work the screen can do.
A kept die does not move and does not change, so the hold a player just made is
still the hold they want, and clearing it was throwing away a decision they had
already expressed.

The selection has to go when the turn does, though. A turn opens with the dice
back in the cup and its first throw must keep nothing -- the rules refuse
anything else -- so a selection carried over from the last turn would be
rejected and Throw would look broken in exactly the way it did before.

Keyed on the round as well as the seat, because a solo game never changes seat:
turn stays at zero and only the round moves on.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Urn6eEBA6XzrnfoibL7faC

app/src/main/java/org/prolibertate/games/ui/game/YahtzeeScreen.kt

@@ -20,6 +20,7 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateListOf
@@ -82,6 +83,11 @@ fun YahtzeeScreen(
         return
     }
 
+    // A turn starts with the dice back in the cup, and its first throw must
+    // keep nothing — a selection carried over from the last turn would be
+    // refused, and the Throw button would look broken again.
+    LaunchedEffect(current.turn, current.round) { kept.clear() }
+
     val yours = current.turn == localSeat && !current.isOver
     val canRoll = legal.any { it is RollDice }
     val writable = legal.filterIsInstance<ScoreIn>().map { it.category }.toSet()
@@ -114,9 +120,11 @@ fun YahtzeeScreen(
                 Button(
                     onClick = {
                         controller.submit(RollDice(kept.toSet()))
-                        // What was kept applied to the throw just made; the next
+                        // The selection stays. A kept die does not move or
-                        // one starts from whatever is on the table now.
+                        // change, so the hold a player just made is still the
-                        kept.clear()
+                        // hold they want — asking them to pick the same three
+                        // again between every throw is work the screen can do
+                        // for them.
                     },
                 ) {
                     Text(if (current.hasRolled) "Throw the rest" else "Throw")