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

tests/libslic3r/test_caddocument.cpp

@@ -2347,12 +2347,12 @@ TEST_CASE("a truncated feature keeps what it could read", "[CadDocument][recipe]
     }
 
     // Shorten feature 1 so it ends right after coordsys_face_kind: drop coordsys_face_edges
-    // (4 bytes) and the two flags appended after it (thread_major_nominal, pattern_inclusive:
-    // 1 byte each). Rewrite its length prefix and erase the tail bytes. The reader then runs
-    // out inside fa(f), throws, and keeps everything it had already assigned — that is the
-    // whole point of the try/catch. (Cut on a field boundary: a field cut in half is read as
-    // whatever half arrived.)
-    const size_t drop = sizeof(uint32_t) + 2 * sizeof(bool);
+    // (4 bytes), the two flags appended after it (thread_major_nominal, pattern_inclusive:
+    // 1 byte each) and the empty dressup_edges list (its 8-byte size tag). Rewrite its length
+    // prefix and erase the tail bytes. The reader then runs out inside fa(f), throws, and keeps
+    // everything it had already assigned — that is the whole point of the try/catch. (Cut on a
+    // field boundary: a field cut in half is read as whatever half arrived.)
+    const size_t drop = sizeof(uint32_t) + 2 * sizeof(bool) + sizeof(cereal::size_type);
     REQUIRE(f_len[1] > drop);
     std::string shortened = blob;
     shortened.erase(f_off[1] + 4 + f_len[1] - drop, drop);
@@ -2370,6 +2370,7 @@ TEST_CASE("a truncated feature keeps what it could read", "[CadDocument][recipe]
     REQUIRE(loaded.features[1].coordsys_face_edges == -1);    // defaulted by the cut
     REQUIRE_FALSE(loaded.features[1].thread_major_nominal);   // ...and so were the later flags
     REQUIRE_FALSE(loaded.features[1].pattern_inclusive);
+    REQUIRE(loaded.features[1].dressup_edges.empty());
     REQUIRE(loaded.features[0].name == doc.features[0].name);
     REQUIRE(loaded.features[2].name == doc.features[2].name);
 }
@@ -7986,6 +7987,87 @@ TEST_CASE("dressup: four chamfer ids captured up-front drift as earlier chamfers
     REQUIRE(ok);
 }
 
+// Several picked edges dressed by ONE feature: every id is resolved against the same body, so
+// capturing them up-front is correct here (unlike the chain of single-edge features above).
+TEST_CASE("dressup: one fillet on four picked edges equals the Top face group", "[CadDocument][dressup]")
+{
+    const double half = 10.0, h = 10.0, r = 1.0;
+    CadDocument doc = make_centred_box(half, h);
+    REQUIRE(doc.recompute());
+    const double v0 = solid_volume(doc.bodies[0].shape);
+
+    std::vector<int> ids;
+    for (const Vec3d& t : { Vec3d(half, 0.0, h), Vec3d(0.0, half, h), Vec3d(-half, 0.0, h), Vec3d(0.0, -half, h) }) {
+        const int id = edge_near(doc.bodies[0].shape, t, 1.5);
+        REQUIRE(id >= 0);
+        ids.push_back(id);
+    }
+    const int fi = doc.add_fillet(r, ids, "Fillet");
+    REQUIRE(doc.features[fi].dressup_edges == ids);
+    REQUIRE(doc.features[fi].dressup_edge == ids.front());   // what an older build falls back to
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double v_list = solid_volume(doc.bodies[0].shape);
+
+    CadDocument ref = make_centred_box(half, h);
+    ref.add_fillet(r, FaceGroup::Top, "Fillet");
+    REQUIRE(ref.recompute());
+    const double v_group = solid_volume(ref.bodies[0].shape);
+
+    INFO("v0=" << v0 << " list=" << v_list << " group=" << v_group);
+    REQUIRE(v_list < v0);
+    REQUIRE(std::abs(v_list - v_group) < 1e-6 * v0);
+
+    SECTION("the list survives a save and load") {
+        const std::string blob = doc.serialize_recipe();
+        CadDocument back;
+        REQUIRE(back.deserialize_recipe(blob));
+        REQUIRE(back.features.size() == doc.features.size());
+        REQUIRE(back.features[fi].dressup_edges == ids);
+        REQUIRE(std::abs(solid_volume(back.bodies[0].shape) - v_list) < 1e-6 * v0);
+    }
+}
+
+TEST_CASE("dressup: one chamfer on two picked edges, a single id still takes the one-edge path", "[CadDocument][dressup]")
+{
+    const double half = 10.0, h = 10.0, d = 0.5;
+    CadDocument doc = make_centred_box(half, h);
+    REQUIRE(doc.recompute());
+    const double v0 = solid_volume(doc.bodies[0].shape);
+    const int a = edge_near(doc.bodies[0].shape, Vec3d(half, 0.0, h), 1.5);
+    const int b = edge_near(doc.bodies[0].shape, Vec3d(-half, 0.0, h), 1.5);
+    REQUIRE(a >= 0);
+    REQUIRE(b >= 0);
+
+    CadDocument one = make_centred_box(half, h);
+    REQUIRE(one.recompute());
+    const int f1 = one.add_chamfer(d, std::vector<int>{ a }, "Chamfer");
+    REQUIRE(one.features[f1].dressup_edges.empty());       // a single pick stays a plain edge feature
+    REQUIRE(one.features[f1].dressup_edge == a);
+    REQUIRE(one.recompute());
+    const double single = v0 - solid_volume(one.bodies[0].shape);
+
+    doc.add_chamfer(d, std::vector<int>{ a, b }, "Chamfer");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double both = v0 - solid_volume(doc.bodies[0].shape);
+    INFO("single=" << single << " both=" << both);
+    REQUIRE(single > 0.0);
+    // Two opposite rim edges share no corner: removing both takes exactly twice one.
+    REQUIRE(std::abs(both - 2.0 * single) < 1e-6 * v0);
+}
+
+TEST_CASE("dressup: an edge list naming a missing edge fails with a reason", "[CadDocument][dressup]")
+{
+    CadDocument doc = make_centred_box(10.0, 10.0);
+    REQUIRE(doc.recompute());
+    const int good = edge_near(doc.bodies[0].shape, Vec3d(10.0, 0.0, 10.0), 1.5);
+    REQUIRE(good >= 0);
+    doc.add_fillet(1.0, std::vector<int>{ good, 9999 }, "Fillet");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_FALSE(doc.error.empty());
+}
+
 // --- Face-drift fingerprint: a FaceAndDirection connector warns when its face index slides ---
 
 TEST_CASE("a connector records its face fingerprint on first recompute", "[CadDocument][mate]")