Consolidate extension forward declarations into extensions/fwd.h

Remove unused `using namespace Extensions` from isleapp.cpp and replace
per-header forward declaration blocks in 7 LEGO1 headers with a single
shared forward declarations header.

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

ISLE/isleapp.cpp

@@ -92,8 +92,6 @@
 #include <psp2/kernel/clib.h>
 #endif
 
-using namespace Extensions;
-
 DECOMP_SIZE_ASSERT(IsleApp, 0x8c)
 
 // GLOBAL: ISLE 0x410030

LEGO1/lego/legoomni/include/isle.h

@@ -2,6 +2,7 @@
 #define ISLE_H
 
 #include "actionsfwd.h"
+#include "extensions/fwd.h"
 #include "legogamestate.h"
 #include "legonamedplane.h"
 #include "legostate.h"
@@ -23,11 +24,6 @@ class RaceCar;
 class SkateBoard;
 class TowTrack;
 
-namespace Multiplayer
-{
-class WorldStateSync;
-}
-
 // VTABLE: LEGO1 0x100d7028
 // VTABLE: BETA10 0x101b9d40
 // SIZE 0x26c

LEGO1/lego/legoomni/include/legoanimationmanager.h

@@ -2,6 +2,7 @@
 #define LEGOANIMATIONMANAGER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "lego1_export.h"
 #include "legolocations.h"
 #include "legomain.h"
@@ -20,10 +21,6 @@ class LegoROIList;
 struct LegoOrientedEdge;
 class LegoWorld;
 class MxDSAction;
-namespace Multiplayer
-{
-class NetworkManager;
-}
 
 // SIZE 0x30
 struct ModelInfo {

LEGO1/lego/legoomni/include/legobuildingmanager.h

@@ -2,6 +2,7 @@
 #define LEGOBUILDINGMANAGER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "lego1_export.h"
 #include "misc/legotypes.h"
 #include "mxcore.h"
@@ -12,10 +13,6 @@ class LegoStorage;
 class LegoWorld;
 class LegoCacheSound;
 class LegoPathBoundary;
-namespace Multiplayer
-{
-class WorldStateSync;
-}
 
 // SIZE 0x2c
 struct LegoBuildingInfo {

LEGO1/lego/legoomni/include/legocharactermanager.h

@@ -2,6 +2,7 @@
 #define LEGOCHARACTERMANAGER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "mxstl/stlcompat.h"
 #include "mxtypes.h"
 #include "mxvariable.h"
@@ -13,13 +14,6 @@ class LegoActor;
 class LegoExtraActor;
 class LegoStorage;
 class LegoROI;
-namespace Extensions
-{
-namespace Common
-{
-class CharacterCloner;
-}
-} // namespace Extensions
 
 #pragma warning(disable : 4237)
 

LEGO1/lego/legoomni/include/legoinputmanager.h

@@ -2,6 +2,7 @@
 #define LEGOINPUTMANAGER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "lego1_export.h"
 #include "legoeventnotificationparam.h"
 #include "mxlist.h"
@@ -26,11 +27,6 @@ class LegoCameraController;
 class LegoControlManager;
 class LegoWorld;
 
-namespace Extensions
-{
-class MultiplayerExt;
-}
-
 extern MxS32 g_clickedObjectId;
 extern const char* g_clickedAtom;
 

LEGO1/lego/legoomni/include/legonavcontroller.h

@@ -2,18 +2,12 @@
 #define __LEGONAVCONTROLLER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "mxcore.h"
 #include "mxtypes.h"
 
 struct LegoLocation;
 class Vector3;
-namespace Extensions
-{
-namespace ThirdPersonCamera
-{
-class OrbitCamera;
-}
-} // namespace Extensions
 
 //////////////////////////////////////////////////////////////////////////////
 //

LEGO1/lego/legoomni/include/legoplantmanager.h

@@ -2,6 +2,7 @@
 #define LEGOPLANTMANAGER_H
 
 #include "decomp.h"
+#include "extensions/fwd.h"
 #include "legomain.h"
 #include "mxcore.h"
 
@@ -11,10 +12,6 @@ struct LegoPlantInfo;
 class LegoROI;
 class LegoStorage;
 class LegoWorld;
-namespace Multiplayer
-{
-class WorldStateSync;
-}
 
 // VTABLE: LEGO1 0x100d6758
 // SIZE 0x2c

extensions/include/extensions/fwd.h

@@ -0,0 +1,23 @@
+#ifndef EXTENSIONS_FWD_H
+#define EXTENSIONS_FWD_H
+
+namespace Extensions
+{
+class MultiplayerExt;
+namespace Common
+{
+class CharacterCloner;
+}
+namespace ThirdPersonCamera
+{
+class OrbitCamera;
+}
+} // namespace Extensions
+
+namespace Multiplayer
+{
+class NetworkManager;
+class WorldStateSync;
+} // namespace Multiplayer
+
+#endif // EXTENSIONS_FWD_H