v0.65.0

Agent endpoints (SCR-443): agent.quote() (credits, USD, parameter validation, latency), agent.feedback() / agent.reportBug(), results.get() (free re-read of a billed result with jq/fields/max_items/summary), requests.get() (poll a Prefer: respond-async call), and an AgentTrial type for account/me. Additions only; no existing signature changed.