[NaySurGithub]

Summary

Adds the API for WebAssembly plugins next to the other languages:

• wasm/falcon.wit (falcon:plugin@1.3.3): the plugin API in WIT, mirroring falcon_api.h except runAsync (a Wasm store must never be entered from two threads)
• wasm/c/falcon_wasm.{h,c}: a small C layer over the wit-bindgen C bindings, so a plugin only writes falcon_enable() and its handlers
• examples/wasm/HelloWasm: a complete plugin of about 20 lines, built with its build.sh (needs wit-bindgen, clang with the wasm32 target and a WASI sysroot)

The server side is Falcon-MC/Falcon#26.

Not verified

The Wasm example is not built by CI; it was built locally on macOS arm64 with Homebrew clang and wasi-libc.

Test plan

Run examples/wasm/HelloWasm/build.sh with WASI_SYSROOT set, put build/HelloWasm.wasm and plugin.json in plugins/HelloWasm/ on a server with #26, start it: "HelloWasm is enabled" is logged and /hellowasm answers "Hello from WebAssembly!".

AI disclosure

Prepared with Claude Opus 5.5.