Add WebGPU Wasm bindings and BitonicSortWasm demo

[bmedina]

Summary

• Adds Swift WebGPU bindings for WebAssembly using JavaScriptKit's BridgeJS @JSClass/@JSFunction/@JSGetter macros to wrap browser WebGPU APIs (device, pipelines, buffers, encoders, bind groups, textures, etc.). Note that these are manually-coded bindings, and we may migrate to codegen'd bindings in the future. This is just enough to get the demo working.
• Adds BitonicSortWasm demo, ported from the native BitonicSort demo. This demo can be built and run via:

SWAN_WASM=1 swift package --swift-sdk DEVELOPMENT-SNAPSHOT-2026-02-06-a-wasm32-unknown-wasip1 js --product BitonicSortWasm
python3 -m http.server 3000
open http://localhost:3000/Demos/BitonicSortWasm/index.html

• Adds JavaScriptKit dependency to the just-released 0.46.0 to access the new BridgeJS macros
• Wires WebGPUWasm into the existing WebGPU umbrella target, so consumers can import WebGPU on both native and Wasm

Note that the BitonicSortWasm code is copied-and-tweaked from the native version. Next step is to unify the code between the two as much as possible.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[cuberoot]

For other projects to use Swan as a dependency, we need the files checked in. I'm wondering if there's any way we can detect when they are out-of-date in CI or something?

[bmedina]

Yes, these are checked in. I'd like to see how the workflow ends up working for folks before adding more automation, but I agree that it may be necessary.

[cuberoot]

This looks like a great step forward. Unifying the APIs will be challenging, but it's great to have this stepping stone.