fix(cli): restore list category fallback for unknown providers
firecrawl list shopping probes shopping as a provider before trying it as a category. The API now rejects unknown providers, so that error previously stopped the category fallback.
Allow the existing fallback for the unknown-provider code or the API's specific unknown/unavailable-provider message. Preserve provider-first precedence and continue surfacing rate-limit, authentication, transport and other errors. No API or version changes.
Validation: TypeScript build, formatting, and compiled CLI regression against a local API fixture. The regression checks the reported shopping failure and that rate-limit errors do not trigger fallback.
Summary by cubic
Restores the category fallback in firecrawl list so commands like firecrawl list shopping still work when the API rejects unknown providers.
Previously, the API's unknown-provider error stopped the existing category fallback, so browsing a category by name failed. Now the fallback proceeds when the API reports an unknown or unavailable provider, while rate-limit, authentication, transport, and other errors still surface as failures. Provider-first precedence is unchanged, and there are no API or version changes.