WebGPU capability check

The platform's distributed training architecture splits on WebGPU (teacher inference, large quantized models) + WASM (student training, ORT-Web TrainingSession) per docs/future-work/WEBGPU-TRAINING-FEASIBILITY.md. This page tells you whether this browser is eligible for the WebGPU half. It runs a tiny vector-add compute shader end-to-end and reports the adapter's actual buffer/binding limits — what the spec promises in theory vs what your machine will actually allocate.