test(erc8004): cover metadata revert propagation

[bussyjd]

Summary

• Add focused coverage for the ERC-8004 setMetadata transaction revert path observed during Flow 11.
• Assert SetMetadata surfaces the exact wrapped error: erc8004: setMetadata tx: execution reverted.

Validation

• go test ./internal/erc8004 ./internal/x402 ./internal/serviceoffercontroller

Notes

• This is intentionally separated from PR release: merge v0.8.0-rc3 integration branch to main #335. Base is feat/x402-buy-side-integration; head is test/erc8004-metadata-revert-coverage.