Context Webhook Endpoint

Telnyx dynamic_variables_webhook_url — called at CONVERSATION START. Returns per-call context (caller identity + live availability + facility info) wrapped under a top-level `dynamic_variables` object (Telnyx requires this), so the fast model skips a mid-call tool round-trip. Task 13 live-pin: confirm exact dynamic-variables webhook request shape (assistant_id + caller number field paths). We parse defensively across the shapes Telnyx may send and pull the assistant id + caller number.

curl -X POST "https://example.com/api/voice/v1/context" \  -H "Content-Type: application/json" \  -d '{}'

{  "dynamic_variables": {}}

{  "detail": [    {      "ctx": {},      "input": null,      "loc": [        "string"      ],      "msg": "string",      "type": "string"    }  ]}