feat(llm/claude): implement list_models_remote via GET /v1/models

[bug-ops]

Parent Epic

#991

Depends On

#992

Summary

Override list_models_remote in ClaudeProvider to query the Anthropic models API.

Endpoint

GET https://api.anthropic.com/v1/models
Authorization: x-api-key: {api_key}
anthropic-version: 2023-06-01

Response Shape

{
  "data": [
    {
      "id": "claude-opus-4-6",
      "display_name": "Claude Opus 4.6",
      "created_at": "2025-08-01T00:00:00Z",
      "type": "model"
    }
  ],
  "has_more": false,
  "first_id": "...",
  "last_id": "..."
}

API supports pagination via ?after_id= query parameter.

Implementation Notes

• Paginate until has_more == false, accumulate all pages.
• Map data[].id → ModelInfo::id, data[].display_name → ModelInfo::display_name,
  data[].created_at → ModelInfo::created_at.
• Cache with provider slug "claude".
• Reuse self.client (existing reqwest::Client).
• Filter to only "type": "model" entries if other types appear.

Acceptance Criteria

• Full pagination — all pages are fetched and merged.
• ModelInfo populated with id, display_name, created_at.
• Cached result served within TTL without network call.
• Invalid/expired API key returns LlmError::Auth, does not cache.
• Unit tests with wiremock or similar.