Design tab: pick several solid edges and dress them in one feature

A solid edge could only be picked one at a time, and Fillet/Chamfer took
either that one edge or a whole face group. Rounding three chosen edges
meant three features, whose edge ids each resolve against a body the
previous one had already changed.

- Shift+click (or Ctrl+click) on an edge of the body already picked adds
  it to the selection, or removes it; the same modifiers that extend a
  sketch selection. The whole set is highlighted. A plain click replaces
  it, as before.
- Fillet/Chamfer dresses every picked edge in ONE feature at one size,
  all ids resolved against the same body. The card says "3 edges", the
  status line and the offer header name the count.
- CadFeature gains dressup_edges, appended at the end of the framed
  recipe, so existing projects load and rebuild unchanged. dressup_edge
  keeps the first edge, so an older build opening a newer project still
  dresses that edge instead of falling back to the face group.
- The MCP fillet/chamfer verbs take `edge` as one id or an array.

Tests: a fillet on the four picked top edges equals the Top face group
exactly; the list survives save/load; two opposite chamfers remove
exactly twice one; a missing id fails with a reason. The truncated-
recipe test accounts for the new tail field.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QK4VgguuCAk2hZLWgcjJb9

src/slic3r/GUI/CAD/DesignSketchTool.cpp

@@ -3445,12 +3445,22 @@ void DesignSketchTool::clear_solid_selection()
     m_solid_sel = SolidSel::None;
     m_sel_body = m_sel_face = m_sel_edge = -1;
     m_sel_edge_pts.clear();
+    m_sel_edges_more.clear();
+    m_sel_edges_more_pts.clear();
     // The pre-highlight names a face/edge/vertex by index into a shape that a recompute has just
     // rebuilt, so it expires with the selection it was a promise about. Left behind it would keep
     // glowing on whatever now sits at those indices — a real entity, but not the one meant.
     m_pre = SolidPick{};
 }
 
+std::vector<int> DesignSketchTool::selected_edges() const
+{
+    if (m_solid_sel != SolidSel::Edge || m_sel_edge < 0) return {};
+    std::vector<int> out = m_sel_edges_more;
+    out.push_back(m_sel_edge);
+    return out;
+}
+
 void DesignSketchTool::select_body(int body)
 {
     // Hidden bodies aren't highlighted (the tint overlay would otherwise draw over a
@@ -3463,6 +3473,8 @@ void DesignSketchTool::select_body(int body)
     m_sel_body  = body;
     m_sel_face  = m_sel_edge = -1;
     m_sel_edge_pts.clear();
+    m_sel_edges_more.clear();
+    m_sel_edges_more_pts.clear();
     m_solid_sel = SolidSel::Whole;   // render_solid_highlight tints just this body
 }
 
@@ -3683,6 +3695,42 @@ bool DesignSketchTool::handle_solid_click(GLCanvas3D& canvas, const wxMouseEvent
     const int      prev_body = m_sel_body, prev_face = m_sel_face, prev_edge = m_sel_edge;
     const Vec3d    prev_vtx  = m_sel_vertex_pt;
 
+    // SHIFT/CTRL+CLICK ON AN EDGE BUILDS AN EDGE SET, the same modifiers that extend a sketch
+    // selection. Only edges of the one body already picked: a dress-up acts on one body, and a
+    // set spanning two could not be applied. An edge already in the set leaves it; the last one
+    // leaving clears the selection. No escalation to the whole body here — a modified click is
+    // always about the set.
+    const bool extend = evt.ShiftDown() || evt.ControlDown() || evt.CmdDown();
+    if (extend && p.kind == SolidSel::Edge && prev_kind == SolidSel::Edge && p.body == prev_body) {
+        auto more = std::find(m_sel_edges_more.begin(), m_sel_edges_more.end(), p.edge);
+        if (p.edge == prev_edge) {
+            if (m_sel_edges_more.empty()) {
+                clear_solid_selection();
+            } else {                          // the previous pick becomes the current one
+                m_sel_edge     = m_sel_edges_more.back();
+                m_sel_edge_pts = std::move(m_sel_edges_more_pts.back());
+                m_sel_edges_more.pop_back();
+                m_sel_edges_more_pts.pop_back();
+            }
+        } else if (more != m_sel_edges_more.end()) {
+            const size_t k = size_t(more - m_sel_edges_more.begin());
+            m_sel_edges_more.erase(more);
+            m_sel_edges_more_pts.erase(m_sel_edges_more_pts.begin() + k);
+        } else {
+            m_sel_edges_more.push_back(prev_edge);
+            m_sel_edges_more_pts.push_back(std::move(m_sel_edge_pts));
+            m_sel_edge     = p.edge;
+            m_sel_edge_pts = std::move(p.edge_pts);
+            m_sel_face     = p.face;
+        }
+        dp_pick_trace("edge set -> %zu edge(s), current %d", selected_edges().size(), m_sel_edge);
+        if (on_solid_selection_changed)
+            on_solid_selection_changed(int(m_solid_sel), m_sel_body, m_sel_face, m_sel_edge);
+        return true;
+    }
+    m_sel_edges_more.clear();
+    m_sel_edges_more_pts.clear();
+
     m_sel_body      = p.body;
     m_sel_face      = p.face;
     m_sel_edge      = p.edge;
@@ -3871,6 +3919,9 @@ void DesignSketchTool::render_solid_highlight()
 
     render_solid_sel(m_solid_sel, m_sel_body, m_sel_face, m_sel_edge_pts, m_sel_vertex_pt,
                      sel_cyan, 1.0f);
+    if (m_solid_sel == SolidSel::Edge)
+        for (const std::vector<Vec3d>& pts : m_sel_edges_more_pts)
+            render_solid_sel(SolidSel::Edge, m_sel_body, -1, pts, Vec3d::Zero(), sel_cyan, 1.0f);
 }
 
 // Datum/reference planes (Plane feature) have no solid; draw each as a translucent indigo