Add 14 new IO primitives to boundary.sx: web interop (request-form,
request-json, request-header, request-content-type, request-args-all,
request-form-all, request-headers-all, request-file-name), response
manipulation (set-response-header, set-response-status), ephemeral
state (state-get, state-set!), and timing (now, sleep).
All 19 reference handlers now have :returns type annotations using
types.sx vocabulary. Response meta (headers/status) flows through
context vars, applied by register_route_handlers after execution.
Only SSE endpoint remains in Python (async generator paradigm).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>