Fix spacecraft panel showing for 1 frame then disappearing

- Remove unconditional reset of ui_state.selected_craft_index in render_body_list_ui()
- Only reset ui_state.selected_craft_index to -1 when body is selected
- This prevents panel from disappearing in subsequent frames when spacecraft remains selected

src/ui_renderer.cpp

@@ -123,12 +123,11 @@ void render_body_list_ui(SimulationState* sim, RenderState* render_state, UIStat
     int previous_active = ui_state->body_list_active;
     GuiListView(list_bounds, list_text, &ui_state->body_list_scroll, &ui_state->body_list_active);
 
-    ui_state->selected_craft_index = -1;
-
     // Check if an item was selected
     if (ui_state->body_list_active >= 0 && ui_state->body_list_active != previous_active) {
         if (ui_state->body_list_active < sim->body_count) {
             render_state->selected_body_index = ui_state->body_list_active;
+            ui_state->selected_craft_index = -1;
             render_state->camera_target_enabled = true;
             printf("Camera follow enabled for body: %s\n", sim->bodies[render_state->selected_body_index].name);
         } else {