docs(ecosystem): add Agentcard

[pipeabellos]

Description

Adds Agentcard to the ecosystem page as a Client-Side Integrations partner.

Agentcard gives AI agents one-time virtual cards for card-rail checkout: fund a wallet, set spend caps and human approvals, and the agent mints a fresh single-use card that works at any merchant that accepts cards. It is a complementary card rail alongside x402 machine-native payments, reaching the long tail of merchants that don't yet accept x402 while agents settle on-chain everywhere they can. Wallets are funded via Coinbase CDP Onramp, and agents connect over a remote MCP server, REST API, or CLI.

Follows the "Adding Your Project to the Ecosystem" steps in typescript/site/README.md:

• New directory typescript/site/app/ecosystem/partners-data/agentcard/ with metadata.json

• Logo added at typescript/site/public/logos/agentcard.png

• category set to Client-Side Integrations (one of the allowed categories)

• Website: https://agentcard.sh

• Docs: https://docs.agentcard.sh

Tests

Data-only ecosystem listing (no package code changed):

• metadata.json validated as well-formed JSON with the required fields (name, category, logoUrl, description, websiteUrl)
• category matches an entry in app/ecosystem/data.ts
• logoUrl points to the added public/logos/agentcard.png (512×512)

Checklist

• I have formatted and linted my code
• All new and existing tests pass (no code paths changed; ecosystem data only)
• My commits are signed (required for merge) — happy to sign/rebase if needed
• I added a changelog fragment for user-facing changes (docs/data-only change — no publishable @x402/* package affected, so no Changeset per the fragment guidance)

[cb-heimdall]

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