feat(子弹): 为VectorStar添加分裂逻辑并重构ArrowSeven

为VectorStar子弹添加分裂时的特殊处理逻辑，确保分裂出的新子弹不会被标记为forwarded
将ArrowSeven子弹重命名为ArrowSevenBullet以明确类名，并移除多余空行

scripts/Contents/Bullets/BossAttack/Bear/ArrowSeven.gd

@@ -1,4 +1,5 @@
 extends BulletBase
+class_name ArrowSevenBullet
 
 @export var allColor: GradientTexture1D = null
 
@@ -16,8 +17,6 @@ func spawn():
 	superlight.material = superlight.material.duplicate()
 	trail.process_material = trail.process_material.duplicate()
 	setColor(myColor)
-
-
 func ai():
 	superlight.global_rotation_degrees = 90
 	PresetBulletAI.forward(self, rotation)
@@ -31,7 +30,6 @@ func ai():
 	else:
 		forwarded = true
 
-
 func setColor(color: Color):
 	texture.self_modulate = color
 	var mat: ParticleProcessMaterial = trail.process_material

scripts/Contents/Bullets/VectorStar.gd

@@ -16,3 +16,6 @@ func ai():
 		speed = (timeLived() - forwardTime) / 30
 		if is_instance_valid(tracer):
 			rotation = position.angle_to_point(tracer.getTrackingAnchor())
+func split(newBullet: BulletBase, _index: int, _total: int, _lastBullet: float):
+	if newBullet is VectorStar:
+		newBullet.forwarded = false