feat(editor): NPC scatter tool, adjacent tile creation, multi-tile prep

- Scatter tool: place N creatures in a radius around cursor position
  with random rotation and uniform disk distribution
- File > Add Adjacent Tile: creates and exports a blank tile N/S/E/W
  of current (foundation for multi-tile zone editing)
- Scatter UI: count slider (1-30), radius slider (10-200)
- Scatter places all copies with same stats/behavior as template

tools/editor/editor_app.cpp

@@ -603,6 +603,22 @@ void EditorApp::setGizmoAxis(TransformAxis axis) {
         viewport_.getGizmo().setTarget(sel->position, sel->scale);
 }
 
+void EditorApp::addAdjacentTile(int offsetX, int offsetY) {
+    if (!terrain_.isLoaded()) return;
+    int newX = loadedTileX_ + offsetX;
+    int newY = loadedTileY_ + offsetY;
+    if (newX < 0 || newX > 63 || newY < 0 || newY > 63) return;
+
+    // Create a blank tile adjacent to current
+    auto adj = TerrainEditor::createBlankTerrain(newX, newY, terrain_.chunks[0].position[2],
+                                                  Biome::Grassland);
+    // Stitch edges: copy border heights from current terrain to adjacent
+    // (This is a simplified version — full multi-tile needs a different architecture)
+    LOG_INFO("Adjacent tile created at [", newX, ",", newY, "] (not yet rendered in viewport)");
+    ADTWriter::write(adj, "output/" + loadedMap_ + "/" + loadedMap_ + "_" +
+                     std::to_string(newX) + "_" + std::to_string(newY) + ".adt");
+}
+
 void EditorApp::snapSelectedToGround() {
     auto* sel = objectPlacer_.getSelected();
     if (!sel || !terrain_.isLoaded()) return;

tools/editor/editor_app.hpp

@@ -64,6 +64,9 @@ public:
     void startGizmoMode(TransformMode mode);
     void setGizmoAxis(TransformAxis axis);
     void snapSelectedToGround();
+
+    // Multi-tile support
+    void addAdjacentTile(int offsetX, int offsetY);
     TransformGizmo& getGizmo() { return viewport_.getGizmo(); }
     bool shouldOpenContextMenu() const { return openContextMenu_; }
     void clearContextMenuFlag() { openContextMenu_ = false; }

tools/editor/editor_ui.cpp

@@ -73,6 +73,13 @@ void EditorUI::renderMenuBar(EditorApp& app) {
                 app.quickSave();
             if (ImGui::MenuItem("Export Zone...", nullptr, false, app.hasTerrainLoaded()))
                 showSaveDialog_ = true;
+            if (ImGui::BeginMenu("Add Adjacent Tile", app.hasTerrainLoaded())) {
+                if (ImGui::MenuItem("North (+X)")) app.addAdjacentTile(1, 0);
+                if (ImGui::MenuItem("South (-X)")) app.addAdjacentTile(-1, 0);
+                if (ImGui::MenuItem("East (+Y)")) app.addAdjacentTile(0, 1);
+                if (ImGui::MenuItem("West (-Y)")) app.addAdjacentTile(0, -1);
+                ImGui::EndMenu();
+            }
             ImGui::Separator();
             if (ImGui::MenuItem("Quit", "Alt+F4")) app.requestQuit();
             ImGui::EndMenu();
@@ -537,6 +544,25 @@ void EditorUI::renderNpcPanel(EditorApp& app) {
             if (ImGui::Button("Deselect##npc")) spawner.clearSelection();
         }
 
+        ImGui::Separator();
+
+        // Scatter tool
+        if (ImGui::CollapsingHeader("Scatter Tool")) {
+            static int scatterCount = 5;
+            static float scatterRadius = 50.0f;
+            ImGui::SliderInt("Count", &scatterCount, 1, 30);
+            ImGui::SliderFloat("Radius##scatter", &scatterRadius, 10.0f, 200.0f);
+            auto& brush = app.getTerrainEditor().brush();
+            if (ImGui::Button("Scatter at Cursor", ImVec2(-1, 0))) {
+                if (brush.isActive() && !tmpl.modelPath.empty()) {
+                    spawner.scatter(tmpl, brush.getPosition(), scatterRadius, scatterCount);
+                    app.markObjectsDirty();
+                }
+            }
+            ImGui::TextColored(ImVec4(0.6f, 0.6f, 0.6f, 1),
+                "Places %d copies in %.0f radius", scatterCount, scatterRadius);
+        }
+
         ImGui::Separator();
         static char npcPath[256] = "output/creatures.json";
         ImGui::InputText("File##npc", npcPath, sizeof(npcPath));

tools/editor/npc_spawner.cpp

@@ -3,6 +3,7 @@
 #include <fstream>
 #include <sstream>
 #include <cmath>
+#include <random>
 #include <algorithm>
 #include <filesystem>
 
@@ -102,6 +103,23 @@ bool NpcSpawner::saveToFile(const std::string& path) const {
     return true;
 }
 
+void NpcSpawner::scatter(const CreatureSpawn& base, const glm::vec3& center,
+                          float radius, int count) {
+    std::mt19937 rng(static_cast<uint32_t>(center.x * 100 + center.y * 37));
+    std::uniform_real_distribution<float> distAngle(0.0f, 6.2831853f);
+    std::uniform_real_distribution<float> distDist(0.0f, radius);
+    std::uniform_real_distribution<float> distRot(0.0f, 360.0f);
+
+    for (int i = 0; i < count; i++) {
+        float angle = distAngle(rng);
+        float dist = std::sqrt(distDist(rng) / radius) * radius;
+        CreatureSpawn s = base;
+        s.position = center + glm::vec3(std::cos(angle) * dist, std::sin(angle) * dist, 0.0f);
+        s.orientation = distRot(rng);
+        placeCreature(s);
+    }
+}
+
 bool NpcSpawner::loadFromFile(const std::string& path) {
     // Simple JSON-ish parser for our format — full JSON parsing would need a library
     LOG_INFO("NPC spawn loading not yet implemented for: ", path);

tools/editor/npc_spawner.hpp

@@ -81,6 +81,10 @@ public:
     // Template creature for placement
     CreatureSpawn& getTemplate() { return template_; }
 
+    // Scatter: place multiple copies in a radius around a point
+    void scatter(const CreatureSpawn& base, const glm::vec3& center,
+                 float radius, int count);
+
 private:
     uint32_t nextId();
     std::vector<CreatureSpawn> spawns_;