feat: native Anthropic provider with Claude Code credential auto-discovery

Add Anthropic as a first-class inference provider, bypassing OpenRouter
for direct API access. Uses the native Anthropic SDK with a full format
adapter (same pattern as the codex_responses api_mode).

## Auth (three methods, priority order)
1. ANTHROPIC_API_KEY env var (regular API key, sk-ant-api-*)
2. ANTHROPIC_TOKEN / CLAUDE_CODE_OAUTH_TOKEN env var (setup-token, sk-ant-oat-*)
3. Auto-discovery from ~/.claude/.credentials.json (Claude Code subscription)
   - Reads Claude Code's OAuth credentials
   - Checks token expiry with 60s buffer
   - Setup tokens use Bearer auth + anthropic-beta: oauth-2025-04-20 header
   - Regular API keys use standard x-api-key header

## Changes by file

### New files
- agent/anthropic_adapter.py — Client builder, message/tool/response
  format conversion, Claude Code credential reader, token resolver.
  Handles system prompt extraction, tool_use/tool_result blocks,
  thinking/reasoning, orphaned tool_use cleanup, cache_control.
- tests/test_anthropic_adapter.py — 36 tests covering all adapter logic

### Modified files
- pyproject.toml — Add anthropic>=0.39.0 dependency
- hermes_cli/auth.py — Add 'anthropic' to PROVIDER_REGISTRY with
  three env vars, plus 'claude'/'claude-code' aliases
- hermes_cli/models.py — Add model catalog, labels, aliases, provider order
- hermes_cli/main.py — Add 'anthropic' to --provider CLI choices
- hermes_cli/runtime_provider.py — Add Anthropic branch returning
  api_mode='anthropic_messages' (before generic api_key fallthrough)
- hermes_cli/setup.py — Add Anthropic setup wizard with Claude Code
  credential auto-discovery, model selection, OpenRouter tools prompt
- agent/auxiliary_client.py — Add claude-haiku-4-5 as aux model
- agent/model_metadata.py — Add bare Claude model context lengths
- run_agent.py — Add anthropic_messages api_mode:
  * Client init (Anthropic SDK instead of OpenAI)
  * API call dispatch (_anthropic_client.messages.create)
  * Response validation (content blocks)
  * finish_reason mapping (stop_reason -> finish_reason)
  * Token usage (input_tokens/output_tokens)
  * Response normalization (normalize_anthropic_response)
  * Client interrupt/rebuild
  * Prompt caching auto-enabled for native Anthropic
- tests/test_run_agent.py — Update test_anthropic_base_url_accepted to
  expect native routing, add test_prompt_caching_native_anthropic

pyproject.toml

@@ -13,6 +13,7 @@ license = { text = "MIT" }
 dependencies = [
   # Core
   "openai",
+  "anthropic>=0.39.0",
   "python-dotenv",
   "fire",
   "httpx",