v0.11.0 harden persistence and prepare game replays

internal/server/core/state.go

@@ -5,7 +5,7 @@ type State int
 const (
 	StateOngoing State = iota
 	StatePending       // Computer is calculating a move
-	StateStuck         // Computer is calculating a move
+	StateStuck         // Engine work failed and requires recovery or undo
 	StateWhiteWins
 	StateBlackWins
 	StateDraw
@@ -31,4 +31,31 @@ func (s State) String() string {
 	default:
 		return "unknown"
 	}
-}
+}
+
+// IsTerminal reports whether the game has a durable result. Pending and stuck
+// are operational states and must not be archived as completed games.
+func (s State) IsTerminal() bool {
+	switch s {
+	case StateWhiteWins, StateBlackWins, StateDraw, StateStalemate:
+		return true
+	default:
+		return false
+	}
+}
+
+// Result returns the stable persistence/API value for a terminal state.
+func (s State) Result() (string, bool) {
+	switch s {
+	case StateWhiteWins:
+		return "white_wins", true
+	case StateBlackWins:
+		return "black_wins", true
+	case StateDraw:
+		return "draw", true
+	case StateStalemate:
+		return "stalemate", true
+	default:
+		return "", false
+	}
+}