Read watch events after a cursor, oldest first

Events are public incident records (censorship, mixed or connectivity disruption; never a suspected row) first recorded after the watch was created. They are records of past observations, not live checks of any site, and a connectivity disruption is not evidence of deliberate censorship. Events are kept 30 days. Pass next_cursor back as cursor; the incident list is read about every 5 minutes while any watch exists. 120 feed reads an hour per identity. Inbox notices, when a watch has them on, are extra copies; the feed stays the complete record. Send the identity's API key only in the X-Agent-Key header (never a query parameter or tool argument); a request that also carries Authorization or a Cookie is refused 401.