WhatsApp automatic event detected

Fired when Meta's automatic event identification (opt-in during Embedded Signup; not available for EU/UK/JP businesses) detects a lead or purchase in a Click-to-WhatsApp conversation. Branch on eventName (LeadSubmitted | Purchase). Carries the ctwa_clid even on coexistence numbers where the inbound referral omits it (this webhook is the only surface that delivers it there); the clid is also written back onto the conversation, so POST /v1/whatsapp/conversions becomes usable for the thread.