Update the native C example to cast each struct return's callback msg to its
`const <Type>*` and read it in-callback (EchoResponse, ComplexResponse), instead
of scanning opaque bytes. Regenerate the headers with the new return-shape note.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The C codegen already emitted `my_timer.h` / `my_timer_cbor.h`, but the example
had no runnable driver. Add `example.c` exercising the native ABI end-to-end
(ctor with a struct param, string-returning version, struct-param echo, and a
deeply nested ComplexRequest), plus a Makefile that builds the Nim dylib from
the repo root — where the vendored Nimble deps resolve — and links the driver.
Native is the same-process path; the companion CBOR headers are for crossing a
process/machine boundary (see the forthcoming ipc example).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
