feat(rules): add game-specific metadata attachment and unify match metadata initialization

Added AttachGameMetadata to GameRules interface

Implemented metadata setup for Battleship (phase + readiness flags)

Implemented no-op metadata hook for TicTacToe

Moved generic phase/ready metadata out of MatchInit

Added game/mode metadata to match state

Fixed json:"metadata" tag in MatchState

plugins/modules/match.go

@@ -130,9 +130,9 @@ func (m *GenericMatch) MatchInit(
 		GameOver: false,
 		Metadata: map[string]interface{}{},
 	}
-  state.Metadata["phase"] = "placement"
-  state.Metadata["p0_ready"] = false
-  state.Metadata["p1_ready"] = false
+  state.Metadata["game"] = m.GameName
+  state.Metadata["mode"] = m.Mode
+	m.Rules.AttachGameMetadata(state)
 
 	label := fmt.Sprintf("%s:%s", m.GameName, m.Mode)