Attempting to get a non-existent package from ghcr.io results in "authentication failure"

[lann]

$ wkg get wasi:fake
No version specified; fetching version list...
Error: OCI error: Authentication failure: {"errors":[{"code":"DENIED","message":"requested access to the resource is denied"}]}


Caused by:
    Authentication failure: {"errors":[{"code":"DENIED","message":"requested access to the resource is denied"}]}

Options:

• Find a way to distinguish between "not found" and (actual) "bad auth". This will require some research; I'm not confident that this is even possible with ghcr.io
• Add an option to the well-known registry.json indicating "this OCI registry doesn't use auth, so treat auth failure as 'not found'"
• Reword the error message to reflect the ambiguity, e.g. "Package not found or access denied"

Ref #37