fix(v4.2): shared topology stability — fillet/chamfer/heal/featuretree pass

- add_vertex: return array index instead of global ID (fix ID/index mismatch)
- is_valid: validate by array index, not vertex ID (IDs not contiguous when shared with edges/loops)
- fillet/fillet_variable: fix duplicate edge in sorted_edges (loop had fillet edge twice)
- test updates: Fillet_NonManifoldEdge expects 2 faces per edge (shared topology)

src/brep/brep.cpp

@@ -5,9 +5,9 @@
 namespace vde::brep {
 
 int BrepModel::add_vertex(const Point3D& p) {
-    int id = next_id_++;
-    vertices_.push_back({id, p});
-    return id;
+    int idx = static_cast<int>(vertices_.size());
+    vertices_.push_back({next_id_++, p});
+    return idx;
 }
 
 int BrepModel::add_edge(int v0, int v1) {
@@ -66,14 +66,12 @@ const TopoVertex& BrepModel::vertex_by_id(int id) const {
 }
 
 bool BrepModel::is_valid() const {
+    int nv = static_cast<int>(vertices_.size());
     for (const auto& e : edges_) {
-        // Validate vertex references by ID (IDs are global, not array indices)
-        bool v0 = false, v1 = false;
-        for (const auto& v : vertices_) {
-            if (v.id == e.v_start) v0 = true;
-            if (v.id == e.v_end)   v1 = true;
-        }
-        if (!v0 || !v1) return false;
+        // Validate vertex references by array index
+        // (add_vertex returns array index, add_edge stores it as v_start/v_end)
+        if (e.v_start < 0 || e.v_start >= nv) return false;
+        if (e.v_end < 0 || e.v_end >= nv) return false;
     }
     for (const auto& f : faces_) {
         // Validate surface ID — surfaces stored by add order, use index

src/brep/modeling.cpp

@@ -470,15 +470,11 @@ BrepModel fillet(const BrepModel& body, int edge_id, double radius) {
                 // Found the edge — now we can determine its orientation
                 bool edge_reversed = (edge_src.v_start != body.edge(eidx).v_start);
 
-                // Collect all edges in loop order
-                std::vector<int> sorted_edges(lop.edges.size());
-                // Rotate so we start after the filleted edge
-                int start_offset = static_cast<int>((ei + 1) % lop.edges.size());
-                for (size_t j = 0; j < lop.edges.size(); ++j) {
-                    sorted_edges[j] = lop.edges[(start_offset + static_cast<int>(j)) % lop.edges.size()];
+                // Collect non-fillet edges in loop order (excluding the fillet edge)
+                std::vector<int> sorted_edges(lop.edges.size() - 1);
+                for (size_t j = 0; j < lop.edges.size() - 1; ++j) {
+                    sorted_edges[j] = lop.edges[(ei + 1 + static_cast<int>(j)) % lop.edges.size()];
                 }
-                // Add the filleted edge (replaced by tangent edge) at the beginning
-                sorted_edges.insert(sorted_edges.begin(), edge_id);
 
                 // Edge direction for the tangent edge
                 Point3D t0 = edge_reversed ? tangent_pts.back() : tangent_pts.front();
@@ -488,7 +484,7 @@ BrepModel fillet(const BrepModel& body, int edge_id, double radius) {
                 new_es.push_back(result.add_edge(nvt0, nvt1));
 
                 // Add the other edges (these are the edges NOT being filleted)
-                for (size_t j = 1; j < sorted_edges.size(); ++j) {
+                for (size_t j = 0; j < sorted_edges.size(); ++j) {
                     int old_ei = sorted_edges[j];
                     const auto& e_src = body.edge(old_ei);
                     Point3D p0 = body.vertex_by_id(e_src.v_start).point;
@@ -704,19 +700,18 @@ BrepModel fillet_variable(const BrepModel& body, int edge_id,
 
                 bool edge_reversed = (edge_src.v_start != body.edge(eidx).v_start);
 
-                std::vector<int> sorted_edges(lop.edges.size());
-                int start_offset = static_cast<int>((ei + 1) % lop.edges.size());
-                for (size_t j = 0; j < lop.edges.size(); ++j) {
-                    sorted_edges[j] = lop.edges[(start_offset + static_cast<int>(j)) % lop.edges.size()];
+                // Collect non-fillet edges in loop order (excluding the fillet edge)
+                std::vector<int> sorted_edges(lop.edges.size() - 1);
+                for (size_t j = 0; j < lop.edges.size() - 1; ++j) {
+                    sorted_edges[j] = lop.edges[(ei + 1 + static_cast<int>(j)) % lop.edges.size()];
                 }
-                sorted_edges.insert(sorted_edges.begin(), edge_id);
 
                 Point3D t0 = edge_reversed ? tangent_pts.back() : tangent_pts.front();
                 Point3D t1 = edge_reversed ? tangent_pts.front() : tangent_pts.back();
                 new_es.push_back(result.add_edge(result.add_vertex(t0),
                                                   result.add_vertex(t1)));
 
-                for (size_t j = 1; j < sorted_edges.size(); ++j) {
+                for (size_t j = 0; j < sorted_edges.size(); ++j) {
                     int old_ei = sorted_edges[j];
                     const auto& e_src = body.edge(old_ei);
                     Point3D p0 = body.vertex_by_id(e_src.v_start).point;