docs(anthropic): correct OAuth scope to Max plan + extra usage credits only (#17404)

The previous docs pass (#17399) overstated what Anthropic OAuth works
with. In practice Hermes can only route against a Claude Max plan that
has purchased extra usage credits — the base Max allowance is not
consumed, and Claude Pro is not supported at all. Without Max + extra
credits, users must fall back to an ANTHROPIC_API_KEY (pay-per-token).

Updates the four pages touched in #17399:
- integrations/providers.md
- user-guide/features/credential-pools.md
- reference/environment-variables.md
- getting-started/quickstart.md

website/docs/getting-started/quickstart.md

@@ -70,7 +70,7 @@ Good defaults:
 |----------|-----------|---------------|
 | **Nous Portal** | Subscription-based, zero-config | OAuth login via `hermes model` |
 | **OpenAI Codex** | ChatGPT OAuth, uses Codex models | Device code auth via `hermes model` |
-| **Anthropic** | Claude models directly — Pro/Max subscription (uses your included Claude Code usage) or API key | `hermes model` → OAuth login, or an Anthropic API key |
+| **Anthropic** | Claude models directly — Max plan + extra usage credits (OAuth), or API key for pay-per-token | `hermes model` → OAuth login (requires Max + extra credits), or an Anthropic API key |
 | **OpenRouter** | Multi-provider routing across many models | Enter your API key |
 | **Z.AI** | GLM / Zhipu-hosted models | Set `GLM_API_KEY` / `ZAI_API_KEY` |
 | **Kimi / Moonshot** | Moonshot-hosted coding and chat models | Set `KIMI_API_KEY` |