probeProviderChain describes the chain that would serve a record
without decrypting, building a client or refreshing a token: which
entries hold a credential, in chain order, whether each reads images,
the in-browser OCR opt-in, and where the credential comes from. It
applies the provider-work authority, appends the central Codex only
behind the opt-in, and falls back to the legacy provider only for an
empty chain. hasAnyConfiguredProvider and resolveProviderAvailability
now answer through it.
Marc-André Bombeck
1be2392c81