`x402DelegationProvider` can create invalid delegation chain

If the `parentPermissionContext` delegates to an address other than the signing address (specified by `from` or `account.address`).

At the least we can validate the delegation chain is continuous and throw an error if it is not.

We could also do this in `encodeDelegations` utility, and / or redelegate action.

Start by tracing x402DelegationProvider and the parentPermissionContext handling; the issue also names encodeDelegations and the redelegate action as possible entry points. Verify the delegation chain remains continuous with the signing address from from or account.address, and confirm that an invalid chain produces an error.

Written by the indexing model from the issue text.