feat(cadfs): 补齐核心建模能力并建立代表性回归

- 新增 loft、双向切除、through-all/up-to-next 等 CADFS lowering 与 engine 支持
- 支持多种 reference plane、B-spline profile 和 circular pattern replay
- 保留 transform 历史，并烘焙安全的单源平移/旋转变换
- 改进 selector 绑定、拓扑快照和 pattern 变换处理
- 建立 17 个代表样本的转换、重建与比较回归工具链
- 补充 schema、author guidance、运行时和几何回归测试

backend/agent/skills/cad-engine/SKILL.md

@@ -51,3 +51,16 @@ Help an AI agent generate CAD models through the repository's CDSL engine.
   value shapes in `cdsl_schema.json`. In particular, hole positions must be
   objects such as `{"mm": [u_mm, v_mm, w_mm]}`, never bare coordinate arrays.
 - Preserve the original CDSL and write revisions as separate artifacts.
+
+## CADFS Engine Maintenance
+
+When changing CADFS lowering, the CDSL schema, runtime, geometry adapter,
+selector binding, or their tests, update
+`cadfs_to_cdsl/ENGINE_CAPABILITY_GAPS_PROGRESS.local.md` in the same change.
+
+- Record the end-to-end capability state, remaining semantic boundary, and
+  regression evidence. A successful rebuild is not geometric similarity.
+- Update a capability to completed only when lowering, contract, execution,
+  geometry, and regression coverage all exist.
+- The progress ledger is local development state and is intentionally ignored
+  by Git. Do not add it to a commit.

backend/agent/skills/cdsl-author-guidance/manifest.json

@@ -15,12 +15,15 @@
     {"id": "10-repair-and-best-effort", "file": "10-repair-and-best-effort.md", "title": "10 Repair And Best Effort", "priority": 80, "mandatory": false},
     {"id": "op-extrude-add", "file": "op-extrude-add.md", "title": "Operation Appendix Extrude Add", "priority": 100, "mandatory": true},
     {"id": "op-extrude-cut", "file": "op-extrude-cut.md", "title": "Operation Appendix Extrude Cut", "priority": 100, "mandatory": true},
+    {"id": "op-loft", "file": "op-loft.md", "title": "Operation Appendix Loft", "priority": 100, "mandatory": true},
     {"id": "op-revolve", "file": "op-revolve.md", "title": "Operation Appendix Revolve", "priority": 100, "mandatory": true},
     {"id": "op-hole", "file": "op-hole.md", "title": "Operation Appendix Hole", "priority": 100, "mandatory": true},
     {"id": "op-reference", "file": "op-reference.md", "title": "Operation Appendix Reference", "priority": 100, "mandatory": true},
     {"id": "op-pattern", "file": "op-pattern.md", "title": "Operation Appendix Pattern", "priority": 100, "mandatory": true},
     {"id": "op-finish", "file": "op-finish.md", "title": "Operation Appendix Finish", "priority": 100, "mandatory": true},
-    {"id": "op-sphere", "file": "op-sphere.md", "title": "Operation Appendix Sphere", "priority": 100, "mandatory": true}
+    {"id": "op-sphere", "file": "op-sphere.md", "title": "Operation Appendix Sphere", "priority": 100, "mandatory": true},
+    {"id": "op-primitives", "file": "op-primitives.md", "title": "Operation Appendix Primitives", "priority": 100, "mandatory": true},
+    {"id": "op-thread", "file": "op-thread.md", "title": "Operation Appendix Thread", "priority": 100, "mandatory": true}
   ],
   "phase_sections": {
     "DEFAULT": ["00-author-contract", "03-coordinate-system-and-datums", "09-evidence-visual-review-and-validation"],
@@ -39,6 +42,9 @@
     "extrude_add_blind": ["op-extrude-add"],
     "extrude_add_two_sided": ["op-extrude-add"],
     "extrude_cut_blind": ["op-extrude-cut"],
+    "extrude_cut_two_sided": ["op-extrude-cut"],
+    "extrude_cut_through": ["op-extrude-cut"],
+    "loft_add": ["op-loft"],
     "revolve_add": ["op-revolve"],
     "revolve_cut": ["op-revolve"],
     "hole_blind": ["op-hole"],
@@ -49,8 +55,13 @@
     "reference_axis": ["op-reference"],
     "pattern_linear": ["op-pattern"],
     "pattern_mirror": ["op-pattern"],
+    "pattern_circular": ["op-pattern"],
     "fillet": ["op-finish"],
     "chamfer": ["op-finish"],
-    "sphere_add": ["op-sphere"]
+    "sphere_add": ["op-sphere"],
+    "box_add": ["op-primitives"],
+    "cylinder_add": ["op-primitives"],
+    "thread_add": ["op-thread"],
+    "thread_cut": ["op-thread"]
   }
 }

backend/agent/skills/cdsl-author-guidance/op-extrude-cut.md

@@ -1 +1 @@
-`extrude_cut_blind` 使用闭合草图、当前允许的正距离和正确宿主 frame。从实际材料面进入，方向由 workplane normal 与 contract 的 `reverse` 决定；深度应覆盖目标材料，不能刚好停在共面边界。切除失败时先检查轮廓、宿主、方向、深度和材料覆盖，而不是盲目加大距离。
+`extrude_cut_blind` 使用闭合草图、当前允许的正距离和正确宿主 frame。从实际材料面进入，方向由 workplane normal 与 contract 的 `reverse` 决定；深度应覆盖目标材料，不能刚好停在共面边界。`extrude_cut_two_sided` 必须分别提供正向和反向的距离与终止条件，不能以单侧深度近似双向切除。`extrude_cut_through` 只接受明确的 `end_condition`，由现有主体跨度决定穿透距离，不能伪造盲向深度。切除失败时先检查轮廓、宿主、方向、深度和材料覆盖，而不是盲目加大距离。

backend/agent/skills/cdsl-author-guidance/op-loft.md

@@ -0,0 +1 @@
+`loft_add` 在 `params.profile_sketch_ids` 中按放样方向列出至少两条不同的闭合草图。每条截面必须解析为一条无孔外轮廓；截面拓扑和 workplane frame 必须稳定对应。不要以挤出替代放样，也不要把 selector 选中的实体面当作放样截面，除非 operation contract 明确支持。

backend/agent/skills/cdsl-author-guidance/op-primitives.md

@@ -0,0 +1 @@
+`box_add` 和 `cylinder_add` 是世界坐标原生图元。按 operation contract 提供正尺寸以及明确的 `center_mm` 或 axis。仅在目标确为长方体或圆柱体时使用；由轮廓驱动的几何保留草图、放样等历史表达。

backend/agent/skills/cdsl-author-guidance/op-thread.md

@@ -0,0 +1 @@
+`thread_add` 和 `thread_cut` 需要明确的 axis、正的大小径、螺距和长度，且各参数必须物理一致。螺纹切除必须有已有宿主实体；需求为实体螺纹时，不能以光滑孔替代。