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/specs/cutout-symmetry-seam/spec.md

@@ -66,7 +66,9 @@ Fill Sides 生成的侧壁 SHALL 只连接不落在对称面上的边界边，
 
 ### Requirement: 切边平滑独立控制
 
-`Seam Smooth` SHALL 控制切口环的面内平滑次数，`Fill Smooth` SHALL 控制界外轮廓的面内平滑次数。两者都只移动面内分量并锁定对称轴坐标，影响范围按两圈渐变从中心向内部衰减。侧壁细分 SHALL 始终存在，不以 `Fill Smooth > 0` 为开关。`Seam Smooth` 为 0 SHALL 保持原始切口，`Fill Smooth` 为 0 SHALL 保持原始轮廓；两个参数 SHALL 互不影响，且都与 Fill Sides 独立。
+`Seam Smooth` SHALL 控制切口环的面内平滑次数，`Fill Smooth` SHALL 控制 front 衔接带的面内平滑次数。两者都只移动面内分量并锁定对称轴坐标。侧壁细分 SHALL 始终存在，不以 `Fill Smooth > 0` 为开关。`Seam Smooth` 为 0 SHALL 保持原始切口，`Fill Smooth` 为 0 SHALL 保持原始轮廓；两个参数 SHALL 互不影响，且都与 Fill Sides 独立。
+
+`Seam Smooth` 按切口环的两圈渐变衰减，切口环按 `pinned-geometry-smoothing` 的 `Pin Boundary` 与 `Pin Sharp` 处理。`Fill Smooth` 的锚点 SHALL 是 front 的完整边界带，即界外轮廓与对称面上的切缝，SHALL 按四圈渐变衰减并覆盖对称轴上的点；衔接处不是网格边界，因此 MUST NOT 套用 `Pin Boundary`，只保留 `Pin Sharp`。
 
 #### Scenario: 切边平滑保持切口落在对称面
 
@@ -77,9 +79,15 @@ Fill Sides 生成的侧壁 SHALL 只连接不落在对称面上的边界边，
 #### Scenario: 两个平滑参数互不影响
 
 - **WHEN** 只改变 Fill Smooth 或只改变 Seam Smooth
-- **THEN** 前者只改变界外轮廓及其侧壁，后者只改变切口环及其两圈渐变范围
+- **THEN** 前者只改变衔接带及其侧壁，后者只改变切口环及其两圈渐变范围
 - **AND** Seam Smooth 为 0 时切口保持原始形态，Fill Smooth 为 0 时轮廓保持原始形态且侧壁仍保持细分
 
+#### Scenario: 衔接带覆盖对称轴
+
+- **WHEN** Fill Smooth 大于 0
+- **THEN** 界外轮廓与对称轴上的点都产生面内位移
+- **AND** 位移从完整边界带向内按四圈渐变衰减
+
 #### Scenario: 关闭补面仍可平滑切边
 
 - **WHEN** Fill Sides 关闭且 Seam Smooth 大于 0