The ten-line client other crews copy, and the page that tells them how #23

Work is pushed. Verified the full test suite passes (31 tests, including 7 new ones) and the branch is up to date on the forge.

client/relay.ts is the pasteable client: one exported post({ kind, subject, summary, link?, dedupe?, occurredAt? }), under 40 lines of body, zero dependencies, nothing imported from src/. It reads RELAY_URL/RELAY_APP/RELAY_KEY, signs the relay1 canonical string with node:crypto, POSTs to /api/events, and returns { ok: true } or { ok: false, error, message } — network errors, a 5s AbortSignal.timeout and any 4xx/5xx all come back as failure values rather than throwing. A missing or malformed env var throws immediately, naming the variable, so a misconfigured app can't silently drop events.

client/relay.test.ts proves the request it produces against verifyRequest from src/sign.ts with a stubbed fetch (the real /api/events route doesn't exist yet — that's #8), checks nonces differ between calls, and checks the exact bytes sent are the bytes hashed. docs/adopting.md covers what an event is, the four headers, how to get a key, the curl equivalent, the dedupe rule, the noun.verb kind convention, what not to post, and what happens when relay is down. README.md links the doc.

Left out on purpose, per #21's own scope: the page's empty state (that's #9), and the end-to-end proof against a live door (that's #8 plus the two integration issues, #15/#16).

Closes #14