provider: cloro adapter

[clgtm]

Goal

cloro provider, access scraped. Engine list from public docs, to be corrected against fixtures: chatgpt, ai_mode, perplexity, gemini.

This is a good first contribution. It is one HTTP call, one response parse, and a fixture, written to the interface in docs/providers.md. Expect about 150 lines.

Scope

• Implements Provider; credentials from the env var named in docs/providers.md
• Calls counts billed requests; no currency
• ErrNoAnswerSurface for Google surfaces that did not render
• Recorded fixtures under testdata/, offline tests, optional live test behind //go:build live

Acceptance

• limelit run --target chatgpt:cloro stores an answer with citations
• Offline tests cover a normal answer, a missing surface where applicable, an auth failure
• docs/providers.md engine list for cloro corrected to what the fixtures prove

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Docs: README.md, docs/tools.md, docs/providers.md

[ShruthiNarasimhan]

Hi! I’d like to work on this issue. I’ll implement the Cloro provider against the existing Provider interface, add recorded fixtures and offline tests for the normal response, missing answer surface, and authentication failure cases, and update the documentation based on the engine behavior verified by the fixtures. I’ll also keep the live test optional as described in the issue. Thank you!

[clgtm]

Thanks @ShruthiNarasimhan I've assigned #30 to you.

A couple of pointers:

Please sign off your commits (git commit -s) and run make lint && make test before pushing; CONTRIBUTING.md has the details.

Once this one merges, #31 is yours if you still want it.