JSEP — deprecated

This directory holds the TypeScript half of JSEP, the JavaScript WebGPU compute path. It is deprecated and will be removed. The replacement is the native WebGPU execution provider, already shipping as onnxruntime-web/webgpu and onnxruntime-web/jspi.

Bug fixes and security fixes only. New operators, new features and performance work belong in the native WebGPU EP (onnxruntime/core/providers/webgpu/).

WebNN is not deprecated. backend-webnn.ts and webnn/ live here only because they share JSEP's initialization glue. WebNN is already the native C++ WebNN EP in every build, and this code will be relocated to a neutral path rather than removed.

See docs/JSEP_Deprecation.md for more details.