feat: Add AgentPass identity & credential verification plugin

[kai-agent-free]

Summary

Adds @solana-agent-kit/plugin-agentpass — a plugin for verifying AI agent identities and credentials using AgentPass.

Addresses #531 (Agent Identity Verification Infrastructure)
Related to #542 (AgentID Interoperability)

What it does

Two actions for the agent toolkit:

VERIFY_AGENT_IDENTITY

Verifies an agent's passport via AgentPass API and checks on-chain wallet binding on Solana.

const result = await agent.methods.verify_agent({
  passport_id: "ap_a622a643aa71",
});
// → { verified: true, name: "Kai", onchain_bound: true }

CHECK_AGENT_CREDENTIAL

Checks if an agent has specific verifiable credentials (MVA format) with optional on-chain anchor verification.

const creds = await agent.methods.check_credential({
  passport_id: "ap_a622a643aa71",
  credential_type: "capability",
});

Architecture

• Off-chain: Queries AgentPass API (api.agentpass.space) for passport data and credentials
• On-chain: Checks Solana program PDAs for wallet-passport binding and credential anchors
• Combined: Returns unified verification result

AgentPass Background

• Open-source identity layer for AI agents ("Auth0 for AI Agents")
• 335+ passing tests, production deployment
• MVA Credential standard with 3 verifiers
• On-chain credential anchor program: agentpass-solana
• NIST CAISI RFI submission on agent identity standards

Files

File	Description
src/index.ts	Plugin definition (follows v2 Plugin interface)
src/actions/verifyAgent.ts	VERIFY_AGENT_IDENTITY action
src/actions/checkCredential.ts	CHECK_AGENT_CREDENTIAL action
src/tools/verify_agent.ts	Core identity verification logic
src/tools/check_credential.ts	Core credential check logic

Follows existing plugin conventions (tsup build, peerDependencies, tsconfig extends).