Add Second Opinion (adversarial verification API) to Ecosystem

[secondopinionx402]

Adds Second Opinion to Ecosystem.

What it is: a pay-per-verdict verification API for AI agents. An independent skeptic
model attempts to refute a claim before the calling agent acts on it, returning a
structured verdict (refuted / supported / inconclusive) with calibrated confidence,
findings, and citations.

Live and settling real x402 payments on mainnet since July 2026:

• Rails: Algorand, Base, Solana (USDC), via the GoPlausible facilitator and Coinbase CDP
• Discovery: /.well-known/x402, /v1/schema, /openapi.json, /llms.txt all live
• Zero-install hosted MCP connector at /mcp (custody-free pass-through payments) — settled real verdicts on all three chains through the connector (26–27 Jul 2026); listed in the official MCP Registry as com.secondopinionx402/second-opinion
• Verified listing on x402-list.com (domain-verified, 100% uptime): https://x402-list.com/services/second-opinion-ms0hen6l-0
• Accuracy self-benchmarked AND measured on the public AVeriTeC 500-claim set, failures published: https://secondopinionx402.com/benchmark

One entry, follows the list format, links tested today.