POST /api/v1/agent/resync

curl -X POST https://provenonce.io/api/v1/agent/resync \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer pvn_..." \
  -d '{"action": "challenge"}'

{
  "challenge": {
    "nonce": "a1b2c3d4...",
    "required_beats": 195,
    "start_from_hash": "0xabc...",
    "start_from_beat": 2659,
    "difficulty": 1000,
    "sync_to_global": 2607
  },
  "gap_beats": 177
}

curl -X POST https://provenonce.io/api/v1/agent/resync \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer pvn_..." \
  -d '{
    "action": "prove",
    "challenge_nonce": "a1b2c3d4...",
    "proof": {
      "from_beat": 2659,
      "to_beat": 2854,
      "from_hash": "0xabc...",
      "to_hash": "0xdef...",
      "beats_computed": 195,
      "global_anchor": 2607,
      "anchor_hash": "23f3d41b...",
      "spot_checks": [...]
    }
  }'

{ "ok": true, "status": "active", "total_beats": 2854 }