feat(editor): select all, recent zones, minimap selection highlights

- Ctrl+A selects all placed objects, context menu has Select All item
- selectAll() added to ObjectPlacer, works with multi-select transforms
- Recent Zones submenu in File menu (last 8 loaded zones, deduplicated)
- Minimap: selected objects shown as white dots with gold ring outline
  vs yellow dots for unselected objects
- Help panel updated with Ctrl+A and Ctrl+Shift+Click documentation

tools/editor/editor_app.cpp

@@ -302,6 +302,10 @@ void EditorApp::processEvents() {
                     ui_.openNewTerrainDialog();
                 if (sc == SDL_SCANCODE_O && (event.key.keysym.mod & KMOD_CTRL))
                     ui_.openLoadDialog();
+                if (sc == SDL_SCANCODE_A && (event.key.keysym.mod & KMOD_CTRL)) {
+                    objectPlacer_.selectAll();
+                    showToast("Selected " + std::to_string(objectPlacer_.selectionCount()) + " objects");
+                }
                 // Ctrl+Y = Redo (alternate binding)
                 if (sc == SDL_SCANCODE_Y && (event.key.keysym.mod & KMOD_CTRL)) {
                     if (terrainEditor_.history().canRedo()) {
@@ -699,6 +703,13 @@ void EditorApp::loadADT(const std::string& mapName, int tileX, int tileY) {
     loadedTileX_ = tileX;
     loadedTileY_ = tileY;
 
+    // Track recent zones (deduplicate, max 8)
+    recentZones_.erase(std::remove_if(recentZones_.begin(), recentZones_.end(),
+        [&](const RecentZone& rz) { return rz.mapName == mapName && rz.tileX == tileX && rz.tileY == tileY; }),
+        recentZones_.end());
+    recentZones_.insert(recentZones_.begin(), {mapName, tileX, tileY});
+    if (recentZones_.size() > 8) recentZones_.resize(8);
+
     // Position camera at terrain center using actual chunk positions
     if (mesh.validChunkCount > 0) {
         auto& firstChunk = mesh.chunks[0];