feat(circle_cctp): add Circle Bridge Kit contract address

[dak-agent]

Adds the Circle Bridge Kit contract to mainnet/circle_cctp.jsonc:

• BridgeKit: 0xB3FA262d0fB521cc93bE83d87b322b8A23DAf3F0

Evidence: BlockVision curated label "Circle / Circle Bridge Kit" (verified) for this address on Monad mainnet; deployed via the canonical deterministic CREATE2 deployer (0x4e59b448…), consistent with Circle's multi-chain deployment pattern. Surfaced during the activity-dashboard top-contracts attribution review (rank #121).

python scripts/validate_protocol.py --network mainnet --protocol circle_cctp passes.

[github-actions]

Contract Verification Results

Changed Files

• mainnet/circle_cctp.jsonc

Verification Output

Verifying 1 protocol file(s)...

  ✓ Circle CCTP (5 addresses)

================================================================================
                         CONTRACT VERIFICATION RESULTS                          
================================================================================

✗ Circle CCTP (circle_cctp.jsonc)
  └─ ✓ TokenMessengerV2: 0x28b5a0e9C621a5BadaA536219b3a228C8168cf5d [Verified]
  └─ ✓ MessageTransmitterV2: 0x81D40F21F12A8F0E3252Bccb954D722d4c464B64 [Verified]
  └─ ✓ TokenMinterV2: 0xfd78EE919681417d192449715b2594ab58f5D002 [Verified]
  └─ ✓ MessageV2: 0xec546b6B005471ECf012e5aF77FBeC07e0FD8f78 [Verified]
  └─ ✗ BridgeKit: 0xB3FA262d0fB521cc93bE83d87b322b8A23DAf3F0 [Not verified]

================================================================================
                                    SUMMARY                                     
================================================================================
  Files Processed:     1
  Addresses Checked:   5
  ✓ Verified:          4
  ✗ Not Verified:      1
================================================================================

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_{Workflow run: Verify PR Contracts}