Retrieve an allowlisted governance-discovery placement and short-lived attribution token.

Records the opaque placement, a bounded retrieval identifier, the retrieval kind, a timestamp, and an expiry. The discovery service at beacon.getmarrow.ai also records one of four fixed automation classes derived from bot-verification signals or the User-Agent header. Raw prompts, source code, credentials, personal data, network addresses, and User-Agent text are not stored in discovery metrics. A salted hash of the caller network address is kept temporarily in a separate rate-limit counter.