chore: investigate error message usefulness on thrown walk error

[SgtPooki]

In order to address some usecases for @helia/verified-fetch

https://github.com/ipfs/helia-verified-fetch/blob/696ed5735b99262e27710fa382d0905a42b6a386/packages/verified-fetch/src/utils/walk-path.ts#L18-L35

Do we provide enough information already? are there more details we can provide? (how far did we walk, where in the walk did we fail, etc.)

To close this:

1. decide on improvements to make (if any)
2. document potential error cases in the context of helia/verified-fetch