Add NEX Agent Co. to Partners + Community Spotlight: first live A2A + x402 dual-protocol agent on Base

Hi A2A team — would like to request adding [NEX Agent Co.](https://nexaitechau.github.io/) to:
1. **Partners** (docs/partners.md) — as an official A2A partner
2. **Community Spotlight** (docs/community.md) — as a featured live A2A + x402 dual-protocol implementation

**Why NEX qualifies:**
- **First live A2A + x402 dual-protocol agent in production** on Base mainnet
- Implements both A2A spec and the A2A x402 extension end-to-end (payment-required → payment-submitted → payment-completed)
- 11 paid x402 USDC endpoints at $0.001-0.01 each (chat, code, code-pro, vision, embed, crypto-price, weather, geo, fx, whois)
- 10 free mirrors at /v1/free/* (30/min/IP)
- A2A JSON-RPC 2.0 endpoint at /a2a/tasks/send
- Apache-2.0 reference server: github.com/NEXAITECHAU/nex-x402-server (681 lines, FastAPI + Ollama + x402 v2)
- 23 on-chain NFTs (Identity, Pass, Attestation, Receipt) for ERC-8004-style reputation
- 17 settle_ok events via PayAI facilitator (real on-chain settlements)

**Discovery:**
- A2A card: https://nexaitechau.github.io/agent-card-a2a.json
- x402 manifest: https://charm-preparing-avon-ips.trycloudflare.com/.well-known/x402.json
- Server card: https://charm-preparing-avon-ips.trycloudflare.com/.well-known/agent.json
- A2A Discovery service: https://nexaitechau.github.io/a2a-discovery.html (already indexing 7/13 known agents)
- Live dashboard: https://nexaitechau.github.io/live.html

**Already indexed by:**
google-agentic-commerce/a2a-x402#171, dabit3/a2a-x402-typescript#25, a2aproject/a2a-samples#696, prassanna-ravishankar/a2a-registry#175, anthropics/skills#1699, xpaysh/awesome-x402, Merit-Systems/awesome-agentic-commerce, bitrefill/awesome-agentic-payments#36, michielpost/x402-dev#72, Dhaiwat10/x402-sovereign#3, xpaysh/agentic-economy-boilerplate#3, kyrolabs/awesome-agents#736, VoltAgent/awesome-agent-skills#992, nibzard/awesome-agentic-patterns#149, agentic-commerce-protocol/agentic-commerce-protocol#301, agentcommercekit/ack#186, DefiLlama/DefiLlama-Adapters#20790, ChaosChain/trustless-agents-erc-ri#19, addyosmani/agent-skills#538, lobehub/lobe-chat-agents#1556, MentionNetwork/awesome-agentic-commerce#80, damoahdominic/awesome-agentic-commerce#37.

**Open question for the team:**
What's the process for adding an open-source project to Partners? Is it the same as a corporate partner (PR to docs/partners.md with company info), or is there a separate path for open-source community projects? Happy to ship a clean PR with NEX's listing following the existing format.

The issue asks to add NEX Agent Co. to two documentation files: docs/partners.md and docs/community.md. First, examine the existing format in those files to understand the required structure. Then, prepare a PR adding the provided details (links, description) following that format. Verify the changes locally and ensure the markdown links are correct.

索引モデルが issue の本文から書いたものです。