feat(武器系统): 新增蓝水晶武器及其子弹效果

实现蓝水晶武器系统，包含追踪子弹和环绕钻石效果
- 添加蓝水晶武器及配套子弹资源
- 实现子弹追踪逻辑和钻石环绕效果
- 扩展BulletBase类支持父子弹关联
- 更新角色预设包含新武器

scripts/Contents/Bullets/BlueCrystal.gd

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+extends BulletBase
+class_name BlueCrystalBullet
+
+var tracer: EntityBase = null
+@onready var trail: GPUParticles2D = $%trail
+
+func ai():
+	if is_instance_valid(tracer):
+		var tracker = tracer.getTrackingAnchor()
+		var targetAngle = position.angle_to_point(tracker)
+		trail.rotation = - Vector2.from_angle(rotation).angle_to(Vector2.from_angle(targetAngle)) * 0.75 / (speed / initialSpeed)
+		PresetBulletAI.trace(self, tracker, 0.05)
+	else:
+		trail.rotation = 0
+	speed += 0.1
+	PresetBulletAI.forward(self, rotation)

scripts/Contents/Bullets/BlueCrystal.gd.uid

@@ -0,0 +1 @@
+uid://d1031p38h24tw

scripts/Contents/Bullets/Diamond2.gd

@@ -0,0 +1,6 @@
+extends BulletBase
+class_name Diamond2Bullet
+
+func ai():
+	if is_instance_valid(parent):
+		position = parent.position

scripts/Contents/Bullets/Diamond2.gd.uid

@@ -0,0 +1 @@
+uid://c1ywds8xwerm3