Exercises every route against a running server using the bundled client,
so the request/response path can be checked without the HTTP bridge.
Covers /hello with and without a name, percent- and plus-encoded query
values, text and JSON POST bodies, and the 4.00/4.04/4.05 error paths.
/health is matched by shape rather than an exact string since uptime
moves. Exits non-zero on failure; COAP_HOST/COAP_PORT retarget it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
