Bound enable report with a timeout; clarify API contract docs

reportRepoEnabled runs synchronously on the enable success path, so a backend that accepts the connection but never responds could hang the command after it had already printed success. Wrap it in a 5s timeout.

Also clarify the enable API doc comments: RemoteURL is sent credential- free (not raw), and the CLI deliberately ignores the response fields today (the GitHub App nudge is surfaced by web onboarding).