Adds the services the credential flows need, following the existing
call/fake pattern: a base, an HTTP implementation and a fake for the
vault, the LLM provider catalog and the per-provider credential listing,
registered in all three environments.
The two fakes share an in-memory vault store that reproduces the
server-side rules of the credential listing (owner, active, provider,
soft delete), so a credential created from one panel shows up in the
other exactly as it does against the real backend.
Also teaches extractHttpErrorMessage the RFC 7807 `detail` field, which
is what the execution endpoints answer with.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
