Control a campaign — start, pause, resume or cancel

Drive the lifecycle of a campaign. Send {action: "<verb>"} where verb is one of:

• start — begin dialing (campaign moves draft → running)
• pause — temporarily halt the dialer (running → paused); in-flight calls are allowed to finish
• resume — pick up where it left off (paused → running)
• cancel — stop and finalize (any → cancelled); pending contacts will not be called

Common automation pattern: create campaign → upload CSV → start. Pause/resume is useful when integrating with business hours or external pacing logic.