WACS.WASI.Preview3

WASI Preview 3 (component-model async ABI) host implementations for WACS. Pinned to wasi-0.3.0-rc-2026-03-15. Vertical-slice v0: wasi:cli/run + wasi:cli/{stdin,stdout,stderr} + the stream<u8> bridge to host System.IO.Stream backings. Full end-to-end validation against wit-component-emitted components awaits Preview 3 RC stabilization.