Integrate real EAS on Base for portable reputation (replace MockEAS)

[KryptosAI]

Context

AgentReputation.sol and the SDK reputation extension run against MockEAS.sol. Ratings are not portable and MockEAS emits no Attested event (SDK rateService direct-to-EAS path throws AttestationFailedError against the mock).

Proposed solution

• Use deployed EAS on Base / Base Sepolia (0x4200000000000000000000000000000000000021)
• Register schema: ValuePacketServiceRating(address vendor, address requester, uint8 score, bytes32 transactionId)
• SDK: swap mock assumptions for @ethereum-attestation-service/eas-sdk (MIT); keep MockEAS for anvil-only tests
• Note: SDK rateService attests directly to EAS, so those ratings are not indexed by AgentReputation.getRatings — decide whether to route all ratings through AgentReputation or index EAS attestations

Acceptance criteria

• Schema registered on Base Sepolia (needs deployer gas — maintainer action)
• One end-to-end rating visible on the EAS explorer
• README documents the schema UID

Effort: 3–5 days. Unblocks: witness escrow (ReviewedEscrow).

[KryptosAI]

Deployed. AgentReputation is live on Base Sepolia with real EAS.

Detail	Value
Contract	0x014d6681978A43E0ceCF7BF6474095f7Fa5905f3
EAS	0x4200000000000000000000000000000000000021 ✓
Schema UID	0x6b8489719f85b723636e8761c3ffe829ba7f6ce21e9289c104c0cb97bb405ced
Schema	address provider,address payer,bytes32 channelId,uint8 score,string comment
Schema tx	0xbd2f446b9e7e50ca3ba19881aa659eb75515307da5857f211e184e82fb637f66

Verified E2E: rateService(deployer, channelId=1, score=9, comment) → EAS attestation created (event on 0x420...0021) → getAverageScore returns 9, getRatingCount returns 1.

**This unblocks #3 (ReviewedEscrow).