feat(framework): bump OpenGL 3.3 → 4.3 core context

Cierra 0049b. El context de fn::run_app pide ahora GL 4.3 core con
forward-compat global, habilitando compute shaders, SSBOs, image
load/store y atomic counters — bloques esenciales del graph_renderer GPU
del proyecto osint_graph (issues 0049f y 0049h).

Cambios:

- cpp/framework/app_base.cpp: 4.3 core + forward-compat. Comentario
  marcando que es backward-compatible con shaders #version 330.
- cpp/apps/primitives_gallery/capture.cpp: deja explicitamente 3.3 core
  porque WSL Mesa no entrega 4.3 offscreen (GLXBadFBConfig); ImGui +
  ImPlot funcionan igual en 3.3 para los goldens.
- primitives_gallery: nuevo demo Gfx > gl_info que muestra
  Vendor/Renderer/Version/GLSL en runtime + status 4.3 (verde) +
  limites (MAX_TEXTURE_SIZE, MAX_VERTEX_ATTRIBS, MAX_UNIFORM_BLOCK_SIZE
  y, si 4.3+, MAX_SHADER_STORAGE_BUFFER_BINDINGS y compute shared mem).
  Solo glGetString/glGetIntegerv — sin loader extra.
- About bumped a 0.4.0 con la nota del nuevo demo y de GL 4.3.
- cpp/tests/test_visual.cpp: usa LIBGL_ALWAYS_SOFTWARE=1 al lanzar el
  capture para alinear el driver con update_goldens.sh; sin esto las
  diferencias de strings (llvmpipe vs d3d12) hacen que gl_info supere
  el 1% de tolerancia.
- cpp/tests/golden/gl_info.png: nuevo golden.

Build verificado en Linux (cmake build OK) + Windows cross-compile
(cmake build OK). Las 27 pruebas pasan (incluida test_visual con 42
demos comparadas).

cpp/apps/primitives_gallery/main.cpp

@@ -78,6 +78,7 @@ static const DemoEntry k_demos[] = {
     // Gfx (shaders_lab core)
     {"shader_canvas",   "shader_canvas",   "Gfx",  &gallery::demo_shader_canvas},
     {"gl_texture",      "gl_texture_load", "Gfx",  &gallery::demo_gl_texture},      // wave 1
+    {"gl_info",         "gl_info",         "Gfx",  &gallery::demo_gl_info},         // issue 0049b
 };
 static constexpr int k_demo_count = sizeof(k_demos) / sizeof(k_demos[0]);
 
@@ -205,8 +206,8 @@ int main(int argc, char** argv) {
          .height         = 900,
          .viewports      = true,
          .about          = {.name        = "Primitives Gallery",
-                            .version     = "0.3.0",
-                            .description = "Visual catalog of fn_registry C++ UI primitives. Modo --capture para golden screenshots, sidebar via tree_view, candlestick fix."},
+                            .version     = "0.4.0",
+                            .description = "Visual catalog of fn_registry C++ UI primitives. Now on OpenGL 4.3 core (compute, SSBOs, image load/store) — ver demo gl_info."},
          .init_gl_loader = true},
         render
     );