Add build infrastructure, installer scripts, and fix build errors

- Create vcpkg.json manifest with all editor dependencies
- Create CMakePresets.json for Windows (MSVC) and Linux (GCC)
- Create Inno Setup installer script (setup.iss) with file associations
- Create Windows build helper (build.ps1) with vcpkg auto-install
- Create Linux build/install scripts (build.sh, install.sh)
- Vendor imgui SDL2 backend locally (removed from vcpkg imgui 1.91+)
- Switch CMakeLists.txt from FetchContent to vcpkg find_package
- Fix ElispGenerator missing pure virtual overrides for memory annotations
- Fix Orchestrator::findNodeById const-correctness
- Fix orchestrator_main.cpp loadFile/saveFile type mismatches
- Fix main.cpp SDL_GL_SwapBuffers -> SDL_GL_SwapWindow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

editor/src/main.cpp

@@ -542,7 +542,7 @@ int main(int, char**)
             SDL_GL_MakeCurrent(backup_current_window, backup_current_context);
         }
 
-        SDL_GL_SwapBuffers(window);
+        SDL_GL_SwapWindow(window);
     }
 
     // Cleanup