d337ada4d6
- AST: declFuncIsAsync flag, ekAwait expression kind - Parser: async func declarations, expr.await postfix operator - Sema: allow await anywhere (blocks current thread until task completes) - HIR: ekAwait lowered to bux_task_join(handle) call - C backend: async func emitted as regular function - Example: examples/async.bux + examples_pkg/async project - All 20 existing examples pass, selfhost build works