fix(editor): crater button now click-to-place on terrain

The "Create Crater at Cursor" button used the brush's last hover
position, which was stale by the time the user clicked the button —
the cursor had to move onto the button itself, dragging the brush
position along with it. Result: crater spawned somewhere between
where the user wanted and the button.

New flow: button arms a "click on terrain to place crater" mode
(captures the user's chosen radius/depth/rim at arm time). The next
left-click anywhere on terrain spawns the crater at the actual click
position, regardless of brush state. Button label changes to "ARMED
— click on terrain to place" while waiting, with a Cancel button +
Esc to dismiss.

Misses on terrain leave the mode armed so the user can retry without
re-pressing the button.

tools/editor/editor_app.cpp

@@ -351,6 +351,10 @@ void EditorApp::processEvents() {
                         objectPlacer_.clearSelection();
                         npcSpawner_.clearSelection();
                         ui_.clearPath();
+                        if (pendingCrater_.active) {
+                            pendingCrater_.active = false;
+                            showToast("Crater placement cancelled");
+                        }
                     }
                 }
                 if (sc == SDL_SCANCODE_DELETE) {
@@ -531,6 +535,31 @@ void EditorApp::processEvents() {
                     giz.endDrag();
                     giz.setMode(TransformMode::None);
                 } else if (event.type == SDL_MOUSEBUTTONDOWN) {
+                    // Pending crater placement: take precedence over the
+                    // mode-based click handling below so the next click
+                    // anywhere on terrain spawns the crater instead of
+                    // doing whatever the current mode does.
+                    if (pendingCrater_.active) {
+                        auto ext = window_->getVkContext()->getSwapchainExtent();
+                        rendering::Ray ray = camera_.getCamera().screenToWorldRay(
+                            static_cast<float>(event.button.x),
+                            static_cast<float>(event.button.y),
+                            static_cast<float>(ext.width),
+                            static_cast<float>(ext.height));
+                        glm::vec3 hitPos;
+                        if (terrainEditor_.raycastTerrain(ray, hitPos)) {
+                            terrainEditor_.createCrater(hitPos,
+                                                          pendingCrater_.radius,
+                                                          pendingCrater_.depth,
+                                                          pendingCrater_.rim);
+                            showToast("Crater placed");
+                            pendingCrater_.active = false;
+                        }
+                        // If the click missed terrain, leave the mode armed
+                        // so the user can try again without re-pressing the
+                        // button.
+                        continue;
+                    }
                     // Path point capture (river/road tool)
                     // Alt+click eyedropper in paint mode
                     if (mode_ == EditorMode::Paint && (SDL_GetModState() & KMOD_ALT)) {

tools/editor/editor_app.hpp

@@ -191,6 +191,22 @@ private:
     // reads this so subsequent generations honor the active biome instead of
     // reapplying the same hardcoded heightband textures every time.
     Biome activeBiome_ = Biome::Grassland;
+
+    // "Click on terrain to place crater" mode. The Crater button arms this
+    // with the user's chosen radius/depth/rim; the next left-click on
+    // terrain consumes it and creates the crater at the actual click
+    // position. Solves the UX problem where pressing the button used a
+    // stale brush position because the cursor was on the button itself.
+public:
+    struct PendingCrater {
+        bool active = false;
+        float radius = 30.0f;
+        float depth = 10.0f;
+        float rim = 3.0f;
+    };
+    PendingCrater& pendingCrater() { return pendingCrater_; }
+private:
+    PendingCrater pendingCrater_;
 };
 
 } // namespace editor

tools/editor/editor_ui.cpp

@@ -1236,10 +1236,25 @@ void EditorUI::renderBrushPanel(EditorApp& app) {
             ImGui::SliderFloat("Radius##crater", &craterRadius, 5.0f, 100.0f);
             ImGui::SliderFloat("Depth##crater", &craterDepth, 2.0f, 50.0f);
             ImGui::SliderFloat("Rim Height##crater", &craterRim, 0.0f, 15.0f);
-            auto& brush5 = app.getTerrainEditor().brush();
-            if (ImGui::Button("Create Crater at Cursor", ImVec2(-1, 0)) ) {
-                app.getTerrainEditor().createCrater(brush5.getPosition(), craterRadius, craterDepth, craterRim);
-                app.showToast("Crater created");
+            // Click-to-place: arm pendingCrater so the next left-click on
+            // terrain spawns the crater there, not at the (stale) brush
+            // position that was last set before the cursor moved onto the
+            // button.
+            auto& pc = app.pendingCrater();
+            if (pc.active) {
+                ImGui::TextColored(ImVec4(0.9f, 0.7f, 0.3f, 1),
+                    "ARMED — click on terrain to place");
+                if (ImGui::Button("Cancel##crater", ImVec2(-1, 0))) {
+                    pc.active = false;
+                }
+            } else {
+                if (ImGui::Button("Click on terrain to place crater", ImVec2(-1, 0))) {
+                    pc.active = true;
+                    pc.radius = craterRadius;
+                    pc.depth = craterDepth;
+                    pc.rim = craterRim;
+                    app.showToast("Click on terrain to place crater (Esc to cancel)");
+                }
             }
             ImGui::TextColored(ImVec4(0.6f, 0.6f, 0.6f, 1), "Bowl with raised rim. Fill with water for a lake.");
         }