Independently distributable runtime for RillML.
Implementation modules (archive, handler, handler_package, package,
server) are pub(crate) so that downstream code — including the
rill-runtime and rill-pack binaries, integration tests, and external
crates — depends only on the top-level re-exports declared in this file.
This avoids the dual-module-path problem where both
rill_runtime::handler::wasm::WasmInvokeHandler and
rill_runtime::WasmInvokeHandler would otherwise be part of the 1.x
public API surface. Only the re-export path is stable.