feat(editor): in-editor "Audit Spawns Against Terrain" menu

EditorApp::auditSpawnsAgainstTerrain(threshold) counts every
creature + object whose Z is more than `threshold` yards off the
sampled terrain. Returns the issue count; non-mutating.

Generate menu gets a new "Audit Spawns Against Terrain" item that
runs the audit at the default 5y threshold and shows a toast: a
clean count if everything's fine, or the issue count + a hint to
run "Snap All" if not. Surfaces placement bugs without dropping
to the CLI.

Pairs with the existing "Snap All Spawns to Ground" so the
workflow stays inside the editor: audit → see count → snap →
audit again.

tools/editor/editor_app.cpp

@@ -1830,6 +1830,30 @@ void EditorApp::snapAllSpawnsToGround() {
               std::to_string(snappedO) + " object(s) to ground");
 }
 
+int EditorApp::auditSpawnsAgainstTerrain(float threshold) const {
+    if (!terrain_.isLoaded()) return 0;
+    auto castDown = [&](const glm::vec3& pos, glm::vec3& hit) {
+        rendering::Ray ray;
+        ray.origin = pos + glm::vec3(0, 0, 500);
+        ray.direction = glm::vec3(0, 0, -1);
+        return const_cast<TerrainEditor&>(terrainEditor_).raycastTerrain(ray, hit);
+    };
+    int issues = 0;
+    for (const auto& s : npcSpawner_.getSpawns()) {
+        glm::vec3 hit;
+        if (castDown(s.position, hit)) {
+            if (std::fabs(s.position.z - hit.z) > threshold) issues++;
+        }
+    }
+    for (const auto& o : objectPlacer_.getObjects()) {
+        glm::vec3 hit;
+        if (castDown(o.position, hit)) {
+            if (std::fabs(o.position.z - hit.z) > threshold) issues++;
+        }
+    }
+    return issues;
+}
+
 void EditorApp::clearAllObjects() {
     vkDeviceWaitIdle(window_->getVkContext()->getDevice());
     objectPlacer_.clearAll();

tools/editor/editor_app.hpp

@@ -106,6 +106,11 @@ public:
     // mirror of the --snap-zone-to-ground CLI; useful after terrain
     // edits or random population to fix floating/buried spawns.
     void snapAllSpawnsToGround();
+    // Count spawns whose Z is more than `threshold` yards off from
+    // the terrain. Returns the issue count; 0 means clean. Used by
+    // the in-editor "Audit Spawns" menu to surface placement bugs
+    // without dropping to CLI.
+    int auditSpawnsAgainstTerrain(float threshold = 5.0f) const;
     void centerOnTerrain();
 
     // Multi-tile support

tools/editor/editor_ui.cpp

@@ -403,6 +403,19 @@ void EditorUI::renderMenuBar(EditorApp& app) {
                 ImGui::SetTooltip(
                     "Re-snap every creature + object's Z to actual terrain height.\n"
                     "Run after terrain edits to fix floating/buried spawns.");
+            if (ImGui::MenuItem("Audit Spawns Against Terrain", nullptr, false,
+                                  app.hasTerrainLoaded())) {
+                int issues = app.auditSpawnsAgainstTerrain(5.0f);
+                if (issues == 0)
+                    app.showToast("Audit clean — every spawn within 5y of terrain");
+                else
+                    app.showToast(std::to_string(issues) +
+                                   " spawn(s) more than 5y off terrain — try Snap All");
+            }
+            if (ImGui::IsItemHovered())
+                ImGui::SetTooltip(
+                    "Count spawns whose Z is more than 5y off terrain.\n"
+                    "Surfaces placement bugs without modifying anything.");
             if (ImGui::MenuItem("Clear All Objects/NPCs", nullptr, false, app.hasTerrainLoaded())) {
                 if (app.getObjectPlacer().objectCount() > 0 || app.getNpcSpawner().spawnCount() > 0)
                     app.clearAllObjects();