feat(kotlin-compose): design system + 33 components + gallery_kt + e2e android emulator + scaffolder fixes

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cpp/apps/primitives_gallery/app.md

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+---
+name: primitives_gallery
+lang: cpp
+domain: gfx
+description: "Visual catalog de primitivas C++ UI del fn_registry. Demos por categoria (charts, controls, layout, gl_info). Soporta modo --capture para regresion visual."
+tags: [imgui, gallery, gfx, demo, capture]
+uses_functions: []
+uses_types: []
+framework: "imgui"
+entry_point: "main.cpp"
+dir_path: "cpp/apps/primitives_gallery"
+repo_url: ""
+---
+
+# primitives_gallery
+
+Catalogo visual de las primitivas y componentes ImGui del registry. Cada demo se carga al hacer click en su entrada del sidebar.
+
+## Build & run
+
+```bash
+cd cpp && cmake --build build --target primitives_gallery -j
+./build/primitives_gallery
+```
+
+## Modo capture (regresion visual)
+
+```bash
+./build/primitives_gallery --capture <out_dir>
+```
+
+Renderiza cada demo offscreen y guarda PNGs en `<out_dir>/`. Permite gate visual via golden images.
+
+## Notas
+
+- `auto_dockspace = false` — usa `fullscreen_window` que ocupa todo el viewport.
+- `init_gl_loader = true` — necesario para demos de OpenGL 4.3 core (compute, SSBOs).