fix: harden CLI export without OpenGL thumbnails (#13532)

## Summary
- skip CLI thumbnail generation when an OpenGL/GLFW context cannot be
created, allowing export workflows to continue in headless/automation
environments
- guard filament variant remapping against missing config options and
out-of-range variant indexes
- log warnings instead of dereferencing invalid config state during
CLI/profile-driven export

## Context
These guards came out of automating OrcaSlicer CLI exports for printer
workflows. In that flow, slicing/export can still be valid even when
thumbnail rendering is unavailable, but the current path can proceed
into OpenGL thumbnail setup after context creation fails. Separately,
malformed or mismatched filament/profile state can index past option
vectors during multi-filament value remapping.

## Test plan
- `git diff --check`
- `cmake --build build/arm64 --config RelWithDebInfo --target OrcaSlicer
-- -j4`

src/OrcaSlicer.cpp

@@ -6435,6 +6435,7 @@ int CLI::run(int argc, char **argv)
             glfwGetVersion(&gl_major, &gl_minor, &gl_verbos);
             BOOST_LOG_TRIVIAL(info) << boost::format("opengl version %1%.%2%.%3%")%gl_major %gl_minor %gl_verbos;
 
+            bool thumbnail_opengl_ready = false;
             glfwSetErrorCallback(glfw_callback);
             int ret = glfwInit();
             if (ret == GLFW_FALSE) {
@@ -6463,13 +6464,22 @@ int CLI::run(int argc, char **argv)
                 GLFWwindow* window = glfwCreateWindow(640, 480, "base_window", NULL, NULL);
                 if (window == NULL)
                 {
-                    BOOST_LOG_TRIVIAL(error) << "Failed to create GLFW window" << std::endl;
+                    BOOST_LOG_TRIVIAL(error) << "Failed to create GLFW window; skipping thumbnail rendering for CLI export" << std::endl;
                 }
-                else
+                else {
                     glfwMakeContextCurrent(window);
+                    thumbnail_opengl_ready = true;
+                }
             }
 
             //opengl manager related logic
+            if (!thumbnail_opengl_ready) {
+                BOOST_LOG_TRIVIAL(error) << "OpenGL context unavailable; skip thumbnail generating" << std::endl;
+                need_create_thumbnail_group = false;
+                need_create_no_light_group = false;
+                need_create_top_group = false;
+            }
+            else
             {
                 GUI::OpenGLManager opengl_mgr;
                 bool opengl_valid = opengl_mgr.init_gl(false);