Controlled visual source-generation trial. Do not call shell, browser, web, file-writing, delegation, or image-generation tools. Return the requested complete source directly in your final answer. Do not save files yourself. The evaluator saves your answer verbatim (stripping only a surrounding Markdown fence), supplies the stated libraries, and runs it. You may use an image-reading tool ONLY to inspect the provided reference-plan.png when present. No external assets or network. No evaluator feedback or repair round.

The reference image is ./reference-plan.png. Read it with your image-reading tool.

Return one complete HTML document, no markdown. It must run at 1280x900 and on mobile. Use real Three.js meshes, perspective, lighting and shadows, not a flat screenshot. Use an importmap mapping 'three' to './vendor/three.module.js' and 'three/addons/' to './vendor/addons/'. These are Three.js 0.180.0. Import OrbitControls and GLTFExporter from their standard addon paths. No other libraries, fetch, external assets, fonts, or network. Provide drag-to-orbit, zoom, Reset view, and an Export GLB button that downloads actual binary glTF of the model (not lights, camera or grid). The initial view must show the entire subject. Use English UI labels, refined typography using system fonts, restrained layout, and do not let controls cover the model. Honor prefers-reduced-motion. Expose window.benchmark = {scene, camera, renderer, model, controls} so the evaluator can inspect the real scene; model is the THREE.Group of exportable objects. Name important meshes semantically. Do not use deprecated Three.js APIs. Keep all code self-contained except the provided library files. Reconstruct the attached top-down floor plan as a visually polished furnished 3D room, using the image as the source of positions and counts. Plan coordinates are x right, z down; 1 unit is one meter. Respect all labeled dimensions and coordinates exactly. Use an open-front cutaway so furniture is visible; wall height 2.6 m. Include sofa, desk with a chair, circular table, rug and plant as distinguishable detailed objects. Preserve footprints, relative positions and orientation. Add a Top / Perspective view toggle and a Show dimensions toggle. The supplied plan is a synthetic benchmark, not a photograph; do not invent measurements hidden by perspective. Put a compact factual list of reconstructed coordinates beside the scene.