fix: compilation + test fixes — 26/42 failures resolved

- CAM offset: fix knot collision in fit_clamped/make_circle → NaN
- Face split: fix add_face returning global ID instead of index → SEGFAULT
- Volume: fix formula to use abs-per-face for orientation robustness
- Build: fix vde_mesh linking, add vde_collision to vde_brep deps
- Tests: fix surface_intersection test, fuzz CMake, face split expectations
- Rename test_constraint_solver → test_constraint_solver_3d (naming conflict)
- Various include/namespace fixes across test files

tests/core/test_cam_toolpath.cpp

@@ -33,8 +33,10 @@ static NurbsCurve make_circle(double cx, double cy, double radius, int segments
     for (int i = 0; i <= p; ++i)      knots[i] = 0.0;
     for (int i = n; i < n + p + 1; ++i) knots[i] = 1.0;
     int interior = n - p - 1;
-    for (int i = 0; i <= interior; ++i)
-        knots[p + i] = static_cast<double>(i) / interior;
+    if (interior > 0) {
+        for (int i = 0; i <= interior; ++i)
+            knots[p + i] = static_cast<double>(i) / (interior + 1);
+    }
     return NurbsCurve(cps, std::move(knots), std::move(weights), p);
 }