bonsaiviewer: View Selected Model from the models panel context menu

Right-clicking a model in the models panel now offers "View Selected Model",
which frames the camera on just that model's geometry — View All, scoped to
one model. With several models selected the action reads "View Selected
Models" and frames their union, matching how the panel's existing Move to
Group already treats a multi-selection.

The AABB fold behind viewAll moves into InstanceCompose, which exists so this
kind of logic is unit-testable without a Qt window or a wgpu device (populating
ViewportCore's model map needs a real GPU, so the fold was previously
untestable in place). It splits in two:

- sceneWorldAabb   — every VISIBLE model, what viewAll frames.
- modelsWorldAabb  — only the named models, hidden or not. A model the caller
                     named explicitly is framed even if hidden; second-guessing
                     that is worse than honouring it. Models with no loaded
                     geometry contribute nothing, and if none of them do the
                     camera is left alone rather than flying to the origin.

Both are covered by six new cases in test_instance_compose (131 total).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ifcviewer/tests/test_instance_compose.cpp

@@ -342,3 +342,106 @@ TEST_CASE("findInstanceInModels skips a corrupt instance-index entry", "[instanc
     InstanceCompose::InstanceLookup out;
     REQUIRE_FALSE(InstanceCompose::findInstanceInModels(42u, models, out));
 }
+
+// ---------------------------------------------------------------------------
+// sceneWorldAabb / modelsWorldAabb — the boxes viewAll and "View Selected
+// Model" frame. Both fold per-instance world AABBs; the difference is which
+// models they fold, and that difference is exactly what these pin down.
+// ---------------------------------------------------------------------------
+
+namespace {
+
+// A model holding one instance whose world AABB is the unit box translated to
+// (tx, 0, 0), so each model occupies a distinct, easily-checked slab of space.
+ModelGpuData make_model_at(float tx, bool hidden = false) {
+    ModelGpuData m;
+    m.hidden = hidden;
+    InstanceInfo inst;
+    inst.world_aabb_min[0] = tx - 1.0f;
+    inst.world_aabb_min[1] = -1.0f;
+    inst.world_aabb_min[2] = -1.0f;
+    inst.world_aabb_max[0] = tx + 1.0f;
+    inst.world_aabb_max[1] = 1.0f;
+    inst.world_aabb_max[2] = 1.0f;
+    m.instances.push_back(inst);
+    return m;
+}
+
+} // namespace
+
+TEST_CASE("sceneWorldAabb unions every visible model", "[instance_compose][aabb]") {
+    std::unordered_map<uint32_t, ModelGpuData> models;
+    models.emplace(1u, make_model_at(0.0f));
+    models.emplace(2u, make_model_at(10.0f));
+
+    float mn[3], mx[3];
+    REQUIRE(InstanceCompose::sceneWorldAabb(models, mn, mx));
+    REQUIRE(mn[0] == -1.0f);   // model 1's left face
+    REQUIRE(mx[0] == 11.0f);   // model 2's right face
+}
+
+TEST_CASE("sceneWorldAabb skips hidden models", "[instance_compose][aabb]") {
+    std::unordered_map<uint32_t, ModelGpuData> models;
+    models.emplace(1u, make_model_at(0.0f));
+    models.emplace(2u, make_model_at(10.0f, /*hidden*/true));
+
+    float mn[3], mx[3];
+    REQUIRE(InstanceCompose::sceneWorldAabb(models, mn, mx));
+    REQUIRE(mx[0] == 1.0f);    // the hidden model at x=10 contributed nothing
+}
+
+TEST_CASE("sceneWorldAabb reports empty for a scene with no geometry",
+          "[instance_compose][aabb]") {
+    const std::unordered_map<uint32_t, ModelGpuData> empty;
+    float mn[3], mx[3];
+    REQUIRE_FALSE(InstanceCompose::sceneWorldAabb(empty, mn, mx));
+
+    // A model whose metadata is up but whose instances haven't landed yet is
+    // just as empty — the caller must not frame it.
+    std::unordered_map<uint32_t, ModelGpuData> no_instances;
+    no_instances.emplace(1u, ModelGpuData{});
+    REQUIRE_FALSE(InstanceCompose::sceneWorldAabb(no_instances, mn, mx));
+}
+
+TEST_CASE("modelsWorldAabb folds only the named models", "[instance_compose][aabb]") {
+    std::unordered_map<uint32_t, ModelGpuData> models;
+    models.emplace(1u, make_model_at(0.0f));
+    models.emplace(2u, make_model_at(10.0f));
+    models.emplace(3u, make_model_at(20.0f));
+
+    float mn[3], mx[3];
+    REQUIRE(InstanceCompose::modelsWorldAabb(models, {2u}, mn, mx));
+    REQUIRE(mn[0] == 9.0f);
+    REQUIRE(mx[0] == 11.0f);   // model 2 alone — not the whole scene
+
+    // Several at once unions just those.
+    REQUIRE(InstanceCompose::modelsWorldAabb(models, {1u, 3u}, mn, mx));
+    REQUIRE(mn[0] == -1.0f);
+    REQUIRE(mx[0] == 21.0f);
+}
+
+TEST_CASE("modelsWorldAabb honours a hidden model the caller named",
+          "[instance_compose][aabb]") {
+    // Unlike sceneWorldAabb: "view this model" was asked for explicitly, so a
+    // hidden model still frames rather than silently reporting nothing.
+    std::unordered_map<uint32_t, ModelGpuData> models;
+    models.emplace(1u, make_model_at(10.0f, /*hidden*/true));
+
+    float mn[3], mx[3];
+    REQUIRE(InstanceCompose::modelsWorldAabb(models, {1u}, mn, mx));
+    REQUIRE(mx[0] == 11.0f);
+}
+
+TEST_CASE("modelsWorldAabb reports empty for unloaded / unnamed models",
+          "[instance_compose][aabb]") {
+    std::unordered_map<uint32_t, ModelGpuData> models;
+    models.emplace(1u, make_model_at(0.0f));
+
+    float mn[3], mx[3];
+    REQUIRE_FALSE(InstanceCompose::modelsWorldAabb(models, {}, mn, mx));      // nothing named
+    REQUIRE_FALSE(InstanceCompose::modelsWorldAabb(models, {99u}, mn, mx));   // not loaded
+
+    // A partially-resolvable list still frames what it can.
+    REQUIRE(InstanceCompose::modelsWorldAabb(models, {99u, 1u}, mn, mx));
+    REQUIRE(mx[0] == 1.0f);
+}