Refactor depth surface handling and unify depth sampling rules

- Removed the `always_vertex` parameter from `build_surface_camera` to streamline depth sampling for cutouts and ensure consistent behavior across depth plane and panorama.
- Updated depth sampling logic to ensure that all free boundary points, including the original frame of the depth plane, use neighboring face depth instead of their own texture sampling.
- Adjusted the depth mask deletion process to operate on faces rather than points, eliminating the need for additional cleanup of dangling edges.
- Ensured that the cutout rules are consistently applied across all relevant nodes, removing exceptions and simplifying the logic.
- Updated tests to verify the new behavior, ensuring that cutout points follow the depth of adjacent faces and that the original frame maintains its depth sampling.
- Refactored geometry handling in multiple depth-related nodes to improve clarity and maintainability.

openspec/changes/refine-cutout-symmetry-seam/design.md

@@ -43,11 +43,11 @@
 
 边界判据保持「只有一个相邻面」，再与「顶点越出对称面容差」求交，判断按顶点而非边的平均位置。落在对称面上的切口环在合并后已是共享边，再生成侧壁只会得到退化面或三面共享边。
 
-### 两个两圈渐变平滑
+### 切口环与衔接带两个平滑
 
-`Seam Smooth` 与 `Fill Smooth` 语义对齐 `Boundary Smooth`：都只移动面内分量、锁定对称轴，并都把中心字段模糊两圈形成渐变。
+`Seam Smooth` 与 `Fill Smooth` 都只移动面内分量、锁定对称轴。
 
-`Seam Smooth` 作用于折叠后的切口环，减少切边的面内量化折线；`Fill Smooth` 作用于界外轮廓，即补面的外侧端点，按两圈渐变把轮廓向内部松弛，随后从平滑后的轮廓构建侧壁，因此侧壁自然跟随轮廓。补面的细分始终存在，不再以 `Fill Smooth > 0` 为开关；`Fill Smooth = 0` 只表示不平滑。
+`Seam Smooth` 作用于折叠后的切口环，减少切边的面内量化折线，按两圈渐变衰减，并按 `pinned-geometry-smoothing` 的 `Pin Boundary` 与 `Pin Sharp` 处理。`Fill Smooth` 作用于 front 的衔接带，即界外轮廓与对称面上的切缝共同围出的边界带，按四圈渐变向内松弛，随后从平滑后的轮廓构建侧壁，因此侧壁自然跟随轮廓；衔接处不是网格边界，只保留 `Pin Sharp`。补面的细分始终存在，不再以 `Fill Smooth > 0` 为开关；`Fill Smooth = 0` 只表示不平滑。
 
 两个平滑都在镜像之前完成，两半保持一致，且都与 Fill Sides 无关：关闭补面时 `Fill Smooth` 没有轮廓可作用，`Seam Smooth` 照常作用。