Bugfix toolpath

[ratdoux]

概要

• 当 mixed/MM 涂色区域折叠回同一个物理耗材时，避免对父切片区域进行拆分再合并。
• 仅在启用组件偏置的几何夹紧时，才允许 same-tool/default masks 修改父区域，防止父区域被不必要地碎片化。
• 修复启用 collapsed mixed-filament regions 时，圆形/椭圆表面出现迷宫状、异常弯折走线的问题。

原因

当 mixed filament 区域与父区域使用同一个物理耗材时，same-tool masks 仍然可能触发对父切片区域的布尔拆分和重新合并。这会生成碎片化的小岛，导致本应平滑、笔直的区域出现异常且不必要的复杂走线。

Summary

• Avoid splitting/re-unioning the parent slice when mixed/MM painted masks collapse back to the same physical filament.
• Keep same-tool/default masks from fragmenting the parent region unless component-bias geometry clamping is enabled.
• Fix noisy maze-like toolpaths on rounded/oval surfaces with collapsed mixed-filament regions.

Why

When mixed filament regions shared a physical filament with the parent region, same-tool masks could still force boolean split/reunion work on the parent slice. That produced fragmented islands and strange non-straight toolpaths in areas that should remain smooth.